Improve auto complete

I have done 4 things in this pull request:

1. Update text completer to support unicode characters
2. Fix live autocomplete (this.completers = completers was missing)
3. Rename enableLiveAutocomplete to enableLiveAutocompletion to match with enableBasicAutocompletion so they are more consistent (I hope that is ok. Only the basic one is mentioned in document and since live autocomplete was not working, I hope not many people is using it).
4. Allow the those two settings to take an array of completers besides boolean. Expose text/keyword/snippet completers so user can choose which one they want to use.

This is my first pull request so if I did anything wrong please let me know.

Homa