restructure: move bin/ and tests/ to src/

Also add symlinks from the old `bin/` and `tests/` locations to avoid
breaking scripts and other tools.

Motivations:

  * Scripts and tests no longer have to do dubious things like:

        require('ep_etherpad-lite/node_modules/foo')

    to access packages installed as dependencies in
    `src/package.json`.

  * Plugins can access the backend test helper library in a non-hacky
    way:

        require('ep_etherpad-lite/tests/backend/common')

  * We can delete the top-level `package.json` without breaking our
    ability to lint the files in `bin/` and `tests/`.

    Deleting the top-level `package.json` has downsides: It will cause
    `npm` to print warnings whenever plugins are installed, npm will
    no longer be able to enforce a plugin's peer dependency on
    ep_etherpad-lite, and npm will keep deleting the
    `node_modules/ep_etherpad-lite` symlink that points to `../src`.

    But there are significant upsides to deleting the top-level
    `package.json`: It will drastically speed up plugin installation
    because `npm` doesn't have to recursively walk the dependencies in
    `src/package.json`. Also, deleting the top-level `package.json`
    avoids npm's horrible dependency hoisting behavior (where it moves
    stuff from `src/node_modules/` to the top-level `node_modules/`
    directory). Dependency hoisting causes numerous mysterious
    problems such as silent failures in `npm outdated` and `npm
    update`. Dependency hoisting also breaks plugins that do:

        require('ep_etherpad-lite/node_modules/foo')

src/tests/frontend/specs/select_formatting_buttons.js

@@ -0,0 +1,161 @@
+'use strict';
+
+describe('select formatting buttons when selection has style applied', function () {
+  const STYLES = ['italic', 'bold', 'underline', 'strikethrough'];
+  const SHORTCUT_KEYS = ['I', 'B', 'U', '5']; // italic, bold, underline, strikethrough
+  const FIRST_LINE = 0;
+
+  before(function (cb) {
+    helper.newPad(cb);
+    this.timeout(60000);
+  });
+
+  const applyStyleOnLine = function (style, line) {
+    const chrome$ = helper.padChrome$;
+    selectLine(line);
+    const $formattingButton = chrome$(`.buttonicon-${style}`);
+    $formattingButton.click();
+  };
+
+  const isButtonSelected = function (style) {
+    const chrome$ = helper.padChrome$;
+    const $formattingButton = chrome$(`.buttonicon-${style}`);
+    return $formattingButton.parent().hasClass('selected');
+  };
+
+  const selectLine = function (lineNumber, offsetStart, offsetEnd) {
+    const inner$ = helper.padInner$;
+    const $line = inner$('div').eq(lineNumber);
+    helper.selectLines($line, $line, offsetStart, offsetEnd);
+  };
+
+  const placeCaretOnLine = function (lineNumber) {
+    const inner$ = helper.padInner$;
+    const $line = inner$('div').eq(lineNumber);
+    $line.sendkeys('{leftarrow}');
+  };
+
+  const undo = function () {
+    const $undoButton = helper.padChrome$('.buttonicon-undo');
+    $undoButton.click();
+  };
+
+  const testIfFormattingButtonIsDeselected = function (style) {
+    it(`deselects the ${style} button`, function (done) {
+      helper.waitFor(() => isButtonSelected(style) === false).done(done);
+    });
+  };
+
+  const testIfFormattingButtonIsSelected = function (style) {
+    it(`selects the ${style} button`, function (done) {
+      helper.waitFor(() => isButtonSelected(style)).done(done);
+    });
+  };
+
+  const applyStyleOnLineAndSelectIt = function (line, style, cb) {
+    applyStyleOnLineOnFullLineAndRemoveSelection(line, style, selectLine, cb);
+  };
+
+  const applyStyleOnLineAndPlaceCaretOnit = function (line, style, cb) {
+    applyStyleOnLineOnFullLineAndRemoveSelection(line, style, placeCaretOnLine, cb);
+  };
+
+  const applyStyleOnLineOnFullLineAndRemoveSelection = function (line, style, selectTarget, cb) {
+    // see if line html has changed
+    const inner$ = helper.padInner$;
+    const oldLineHTML = inner$.find('div')[line];
+    applyStyleOnLine(style, line);
+
+    helper.waitFor(() => {
+      const lineHTML = inner$.find('div')[line];
+      return lineHTML !== oldLineHTML;
+    });
+    // remove selection from previous line
+    selectLine(line + 1);
+    // setTimeout(function() {
+    // select the text or place the caret on a position that
+    // has the formatting text applied previously
+    selectTarget(line);
+    cb();
+    // }, 1000);
+  };
+
+  const pressFormattingShortcutOnSelection = function (key) {
+    const inner$ = helper.padInner$;
+
+    // get the first text element out of the inner iframe
+    const $firstTextElement = inner$('div').first();
+
+    // select this text element
+    $firstTextElement.sendkeys('{selectall}');
+
+    const e = new inner$.Event(helper.evtType);
+    e.ctrlKey = true; // Control key
+    e.which = key.charCodeAt(0); // I, U, B, 5
+    inner$('#innerdocbody').trigger(e);
+  };
+
+  STYLES.forEach((style) => {
+    context(`when selection is in a text with ${style} applied`, function () {
+      before(function (done) {
+        this.timeout(4000);
+        applyStyleOnLineAndSelectIt(FIRST_LINE, style, done);
+      });
+
+      after(function () {
+        undo();
+      });
+
+      testIfFormattingButtonIsSelected(style);
+    });
+
+    context(`when caret is in a position with ${style} applied`, function () {
+      before(function (done) {
+        this.timeout(4000);
+        applyStyleOnLineAndPlaceCaretOnit(FIRST_LINE, style, done);
+      });
+
+      after(function () {
+        undo();
+      });
+
+      testIfFormattingButtonIsSelected(style);
+    });
+  });
+
+  context('when user applies a style and the selection does not change', function () {
+    const style = STYLES[0]; // italic
+    before(function () {
+      applyStyleOnLine(style, FIRST_LINE);
+    });
+
+    // clean the style applied
+    after(function () {
+      applyStyleOnLine(style, FIRST_LINE);
+    });
+
+    it('selects the style button', function (done) {
+      expect(isButtonSelected(style)).to.be(true);
+      done();
+    });
+  });
+
+  SHORTCUT_KEYS.forEach((key, index) => {
+    const styleOfTheShortcut = STYLES[index]; // italic, bold, ...
+    context(`when user presses CMD + ${key}`, function () {
+      before(function () {
+        pressFormattingShortcutOnSelection(key);
+      });
+
+      testIfFormattingButtonIsSelected(styleOfTheShortcut);
+
+      context(`and user presses CMD + ${key} again`, function () {
+        before(function () {
+          pressFormattingShortcutOnSelection(key);
+        });
+
+        testIfFormattingButtonIsDeselected(styleOfTheShortcut);
+      });
+    });
+  });
+});