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    problems such as silent failures in `npm outdated` and `npm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/runner.css

@@ -0,0 +1,246 @@
+html {
+  height: 100%;
+}
+
+body {
+  padding: 0px;
+  margin: 0px;
+  height: 100%;
+  display: flex;
+  flex-direction: row;
+  overflow: hidden;
+}
+
+#console {
+  display: none;
+}
+
+#iframe-container {
+  width: 80%;
+  min-width: 820px;
+  height: 100%;
+}
+
+#iframe-container iframe {
+  height: 100%;
+  width:100%;
+}
+
+#mocha {
+  font: 20px/1.5 "Helvetica Neue", Helvetica, Arial, sans-serif;
+  border-right: 2px solid #999;
+  flex: 1 auto;
+  height: 100%;
+  overflow: auto;
+  width:20%;
+  font-size:80%;
+  
+}
+
+#mocha #report {
+  margin: 0;
+  padding: 0;
+  margin-top: 10px;
+}
+
+#mocha li {
+  margin: 0;
+  padding: 0;
+}
+
+#mocha ul {
+  list-style: none;
+}
+
+#mocha h1, #mocha h2 {
+  margin: 0;
+}
+
+#mocha h1 {
+  margin-top: 15px;
+  font-size: 1em;
+  font-weight: 200;
+}
+
+#mocha h1 a:visited
+{
+  color: #00E;
+}
+
+#mocha .suite .suite h1 {
+  margin-top: 0;
+  font-size: .8em;
+}
+
+#mocha h2 {
+  font-size: 12px;
+  font-weight: normal;
+  cursor: pointer;
+}
+
+#mocha .suite {
+  margin-left: 0px;
+}
+
+#mocha .test {
+  margin-left: 5px;
+}
+
+#mocha .test:hover h2::after {
+  position: relative;
+  top: 0;
+  right: -10px;
+  content: '(view source)';
+  font-size: 12px;
+  font-family: arial;
+  color: #888;
+}
+
+#mocha .test.pending:hover h2::after {
+  content: '(pending)';
+  font-family: arial;
+}
+
+#mocha .test.pass.medium .duration {
+  background: #C09853;
+}
+
+#mocha .test.pass.slow .duration {
+  background: #B94A48;
+}
+
+#mocha .test.pass::before {
+  content: '✓';
+  font-size: 12px;
+  display: block;
+  float: left;
+  margin-right: 5px;
+  color: #00d6b2;
+}
+
+#mocha .test.pass .duration {
+  font-size: 9px;
+  margin-left: 5px;
+  padding: 2px 5px;
+  color: white;
+  -webkit-box-shadow: inset 0 1px 1px rgba(0,0,0,.2);
+  -moz-box-shadow: inset 0 1px 1px rgba(0,0,0,.2);
+  box-shadow: inset 0 1px 1px rgba(0,0,0,.2);
+  -webkit-border-radius: 5px;
+  -moz-border-radius: 5px;
+  -ms-border-radius: 5px;
+  -o-border-radius: 5px;
+  border-radius: 5px;
+}
+
+#mocha .test.pass.fast .duration {
+  display: none;
+}
+
+#mocha .test.pending {
+  color: #0b97c4;
+}
+
+#mocha .test.pending::before {
+  content: '◦';
+  color: #0b97c4;
+}
+
+#mocha .test.fail {
+  color: #c00;
+}
+
+#mocha .test.fail pre {
+  color: black;
+}
+
+#mocha .test.fail::before {
+  content: '✖';
+  font-size: 12px;
+  display: block;
+  float: left;
+  margin-right: 5px;
+  color: #c00;
+}
+
+#mocha .test pre.error {
+  color: #c00;
+}
+
+#mocha .test pre {
+  display: inline-block;
+  font: 12px/1.5 monaco, monospace;
+  margin: 5px;
+  padding: 15px;
+  border: 1px solid #eee;
+  border-bottom-color: #ddd;
+  -webkit-border-radius: 3px;
+  -webkit-box-shadow: 0 1px 3px #eee;
+}
+
+#report ul {
+  padding: 0;
+}
+
+#report.pass .test.fail {
+  display: none;
+}
+
+#report.fail .test.pass {
+  display: none;
+}
+
+#error {
+  color: #c00;
+  font-size: 1.5  em;
+  font-weight: 100;
+  letter-spacing: 1px;
+}
+
+#stats {
+  padding: 10px;
+  font-size: 12px;
+  margin: 0;
+  color: #888;
+  text-align: right;
+}
+
+#mocha-stats {
+  height: 80px;
+}
+
+#mocha-stats .progress {
+  float: right;
+  padding-top: 0;
+  margin-right:5px;
+}
+
+#stats em {
+  color: black;
+}
+
+#stats a {
+  text-decoration: none;
+  color: inherit;
+}
+
+#stats a:hover {
+  border-bottom: 1px solid #eee;
+}
+
+#stats li {
+  display: inline-block;
+  margin: 0 5px;
+  list-style: none;
+  padding-top: 11px;
+}
+
+code .comment { color: #ddd }
+code .init { color: #2F6FAD }
+code .string { color: #5890AD }
+code .keyword { color: #8A6343 }
+code .number { color: #2F6FAD }
+
+ul{
+  padding-left:5px;
+}