Travis gamin support on Travis CI

Added _gamin_ support on Travis CI, but only for python2.7. I've therefore also made _coveralls_ only work on python2.7. Could also add _coveralls_ to run on python2.6 with another coveragerc file for Travis CI non-gamin versions, but thought this was a bit unnecessary and getting complex...

@yarikoptic Thanks for your suggestion which made this work.

https://coveralls.io/builds/14277/source?filename=server%2Ffiltergamin.py