Support the Jaikoz 'artists' tag, with help from @night199uk and @zas
Merge branch 'master' of github.com:musicbrainz/picard into artists-tag
Merge branch 'master' of github.com:musicbrainz/picard into artists-tag
Merge branch 'master' of github.com:musicbrainz/picard into artists-tag
PICARD-123: actually use default drive on Mac

This doesn't implement an automatic list of available drives on Mac,
but adds the libdiscid default drive to the list of drive candidates.

This should make disc lookups available on Mac without specifying
the drive (as /dev/rdisk*) in the settings.

Note that setting things like "1" or "2" as drives should also work
with a recent libdiscid. (>= 0.6.0).
use only one definition of get_cdrom_drives()
remove generic try-except

If we do want to catch generic unexpected tracebacks,
this shouldn't be done here.

Note that `import discid` might raise OSError
when the python module is found, but not libdiscid itself.
We might want to catch that explicitely,
but that is supposed to be prevented by whoever made `discid` available.
refactor cdrom code a bit
update NEWS for 123
Merge branch 'master' into always_default_drive

Conflicts:
	picard/util/cdrom.py
Merge pull request #208 from xlotlu/filenaming

updated tests for filename shortening (which now returns relative paths)
Remove extra imports
Update NEWS.txt
Merge branch 'master' into artists-tag

Conflicts:
	NEWS.txt
Merge pull request #188 from mwiencek/artists-tag

Support the Jaikoz 'artists' tag, which stores individual artist names
Fix AttributeError: 'MetadataBox' object has no attribute 'shrink_columns'

shrink_columns() was replaced by resize_columns() in commit 4c64a277cdafd9906a7eb2d7c586383a335a3978
Returns exit code 1 if at least one test failed.

It should make travis-ci to report test failures when they actually fail.
Ie. build 169.1 has test failures, but build was happily reported as Passed,
this patch should change this.
Merge pull request #210 from zas/test_exit_code

Ensure setup.py returns non-zero exit code on test failure
Set up Transifex to pull the country name translations.
Build picard-countries.po for enabled languages.