Replace tabs indentation with spaces indentation

Some files are obviously external libraries, I didn't touch them

tests/frontend/specs/urls_become_clickable.js

@@ -16,7 +16,7 @@ describe("urls", function(){
     firstTextElement.sendkeys('{selectall}'); // select all
     firstTextElement.sendkeys('{del}'); // clear the first line
     firstTextElement.sendkeys('http://etherpad.org'); // insert a URL
-	  
+
     helper.waitFor(function(){
       return inner$("div").first().find("a").length === 1;
     }, 2000).done(done);