Allow using tabs
Hello dear friends.

It think it would be good to add possibility optional using tabs for indentation (turn off and on from settings)
(not to change them to spaces for not to break current indentation levels).

I prefer using them and replacing it during compilation with _#? replace(sub = "\t", by = " ")_ in the top of the file.
Also tab highlighting with red is too disturbing:
![2016-11-02 00-41-23](https://cloud.githubusercontent.com/assets/12682937/19910447/b25a7528-a095-11e6-9eb7-0e19f2c2610e.png)

To distinguish tab and space characters, they could be highlighted like in Atom (GitHub's editor):
![2016-11-02 00-50-15](https://cloud.githubusercontent.com/assets/12682937/19910638/f90880ea-a096-11e6-9bc7-712277347083.png)


Best regards,
Vladislav.