I've just enabled SuperTab in vim, and if I try to indent a blank line, SuperTab is attempting to insert strings. What I'd like, I guess, would be to have SuperTab offer completions only if there is non-whitespace to the left of the cursor.
I don't want to have to use Ctrl-V or Ctrl-Q or anything.
This could be caused by an old version of snipmate, update to the forked version maintained by Gargas.
It has quite a few dependencies so I'd recommend using Vundle if you're not already using it.
See comments to OP for more information.
msanders/snipmate.vim conflicts with supertab.
you can use ultisnips instead of Snipmate
https://github.com/SirVer/ultisnips