Normalize indentation to tabs

Hi again!

I indent HTML with 2 spaces. I noticed that many (most?) of the snippets in here had 4 space indentation, and went about figuring out how to avoid shift-tabbing forever...

According to [the Sublime docs](http://docs.sublimetext.info/en/sublime-text-3/extensibility/snippets.html):

> When writing a snippet that contains indentation, always use tabs. When the snippet is inserted, the tabs will be transformed into spaces if the option translateTabsToSpaces is true.

So, I went through and cleaned up all of the spaces, converting everything to tabs. (Checked every file by hand as there were a few funny 2 and 6 spaced files.) The snippets should work with the user's preferred indentation now...

Thanks!
Matt