fixes #35 - python-coveralls should only be installed in travis

not in tox
#35 - don't install coveralls via pip
probably a typo, I don't think I should be installing both python-coveralls and coveralls via pip. This probably worked because python-coveralls was installed later.
Merge pull request #37 from robdennis/master

fixes #35 - python-coveralls should only be installed in travis