EpicEditor TAB implementation

Issue-159.md

“Smart tabs” sound better, a quick look at configuration files for both vim and sublime text:

Vim 
---
noexpandtab
tabstop
smartindent
smarttab

Sublime Text 
------------
tab_size
translate_tabs_to_spaces
use_tab_stops
...

smarttab in vim is used to respect <BS> character in some circumstances. For example if a tab key is to insert 4 spaces, a <BS> will delete 4 spaces if it is performed after smartindent/expandtab inserts 4 spaces in front of a line.

In the case of EpicEditor, we are combining some of these features into one option:

• Enable tab key (and shift-tab);
• Don't expand tab to spaces (and use css: tab-size instead) – I think expansion of tabs could be useful, but may introduce too many options/variables. But it is something we can discuss: my position is to keep it simple, at least for this first implementation. But I will experiment with this, keen to see how this will work;
• By enabling tab key, we introduce smart indentation (rule where previous lines' indentation is respected).

What I can do is try and experiment with internal options such as smartIndentation, smartTabs, expandTab and see how they pull up together. I am quite keen on seeing how others implement this first.

We can always change the name later on. I'll keep it as smartTabs for now.

I like insertText. And totally makes sense about getSelection. Having tried working with it working with selections is hard and IE vs other browsers handle each differently. A standardized set of tools to handle selections for developers using the API would be awesome.

No rush! Do what you can when you want :)