Adding 2 more and organizing text objects vundles

Hi, although the diff looks ugly, I just did this:

  * Added 2 new text objects: underscore and javascript functions
  * Put all text object vundles into the same visual section in the file.

As a side note: would we be interested in doing this same visual separation for the vundles in the entire file? That is, organize sections for "ruby / rails", "git", "text objetcts" (what i did here),  "languages support" (coffe, R, less, javascript, etc), and so on...

I think it's a nice way to quickly and cleanly see what are we providing there... If you guys like the idea I can start doing that :)