WIP emojis in TextEditor and misc fixes to TextEditor

There are still a few issues to fix:
1) If you select some text and insert a character, the selection isn't replaced by the character (this should be easy to fix)
2) Newlines might cause problems
3) A placeholder image (Mario Bros) is being used instead of the real Emojis
4) On Firefox OS, for some reason, the *word-break: break-all;* rule isn't being respected (http://jsfiddle.net/zz9wn15j/1/)

A problem related to newlines that I'm aware of can be reproduced following these steps:
- Write 'a' (content 'a', innerHTML 'a')
- Press return (content 'a\n', innerHTML 'a< br >< br >')
- Write 'b' (content 'a\nb', innerHTML 'a< br >b< br >')
- Press backspace (content 'a\n', innerHTML 'a< br >') <- Here in *content* we have a newline, but we aren't showing it in the div

(*content* is the variable holding the TextEditor content)
Unfortunately, Chrome doesn't yet support destructuring assignment, so we should avoid it to maintain as much Chrome compatibility as possible, since it can be useful for testing/debugging.