Tabs indented literate files are not supported

[KrysKruk]

Literate CoffeeScript indented using tabs instead of 4 spaces are not supported right now, because the invertLiterate implementation which forces 4 spaces style.

This issue was discussed by @swang and @AsaAyers during the review.

My opinion in this issue:

1. Daring Fireball Markdown Specification says that:

To produce a code block in Markdown, simply indent every line of the block by at least 4 spaces or 1 tab.

1. CoffeeScript parser supports tabs in literate style files.
2. IMHO mixing 4 spaces with 2 spaces or tabs is the worst case scenario.

What do you think guys?