text: Title: Support Mercurial
  Body: I created at PR #155.
  
  I've added a new environment variable called USE_HG, which if set will use mercurial. I mainly left the existing API mostly alone, except two things:
  
  1. I renamed `.git_info` to `.dvcs_info`, which returns the same data structure.
  2. I moved run_command to a new file called utilities.
  2.b `run_command` now supports shell=True `subprocess.Popen`.
  
  I also didn't include remotes for hg, called paths in mercurial, but the concept in mercurial is slightly different, the docs for coveralls don't seem to support it, and I'm not sure what value it adds in any event.
  
  One last bit, I couldn't seem to make non-ascii chars work in the `.hg/hgrc`, so I removed that from the tests.
  
  The USE_HG flag should be documented, but there isn't guidance on how documentation should be added, so I left it alone for now. I'll add it prior to merge - I just would appreciate some guidance.
  
  One last note: `GIT_OR_HG` is all caps because initially I had it as a global var, but this was problematic with the test runner setting the variable on import (git first) and then subsequently failing. I'll change it to lower case whenever someone get's back to me on the documentation bit.
  
  