Initial stab at a Travis configuration file.
Make Travis apt-get libdiscid0.
Remove Python 2.6 from Travis' testing matrix.

Since we rely on apt-get to install PyQt4, it will only be available
for Python 2.7. :(
Also apt-get development files for libdiscid.

This will hopefully make python-libdiscid build.
Have Travis ping #musicbrainz-devel with test results.

Per discussion in pull request #173:
https://github.com/musicbrainz/picard/pull/173

Documentation for further tweaks:
http://about.travis-ci.org/docs/user/notifications/