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/
Add an option in Advanced>Interface to set starting directory.

By default, Picard remembers last directory used and restores it on start,
but this isn't not always desirable, one may prefer to start on the same directory
each time.
This patch allows one to change default behavior and set a starting directory.
Reduce code redundancy and use starting directory for Add folder action