Log release ID for invalid MBIDs
some reorg/docs for FileOperationError
FileOperationError: include underlying exception

A primitive form of Python 3's "exception chaining", which is what we really
want here. Someday...
FileOperationError: also include the file path

This makes the errors fully self-descriptive, which simplifies logging them as
errors (you just have to `log.error(exc)` to get a reasonable message). We
also now handle these at the top level in case someone forgets to add a
handler. But in this case, we also send the full traceback to the debug log.
don't wrap standard errors during Mutagen save()
Add completion script template to dist
Only use primary artist aliases. Fixes #632.

MusicBrainz will send down various artist aliases that may not be the primary
(e.g. the previous name for a group). Only use an alias for the artist if it is
the primary alias in one of the import locales.
Update tests given new alias behavior
Merge pull request #633 from sampsyo/issue-632

Only use primary artist aliases. Fixes #632.
changelog for #632
Add badges of travis and coverage to README
Add irc notifications by travis
Merge pull request #635 from skeuomorf/badges

Add badges of travis and coverage to README
Merge pull request #636 from skeuomorf/notifications

Add irc notifications by travis
Modify command: ability to delete/reset an attribute (beet modify field!)
Merge pull request #638 from brilnius/ui_del_attr2

Modify command: ability to delete/reset an attribute (beet modify field!)
use the new python enum instead of hand-rolled version
add enum34 to install_requirments
Make mediafile tests independent of image order

For MP3s mutagen stores image tags in a hash with the `APIC:...` key. The order
of the images is therefore not well defined. A similar issue occurs with WMAs.
Use tox to test on travis and add docs and flake8

Travis CI now also confirm that the docs build correctly and the flake8 runs
succesfully. Tox also has the advantage that it tests that beets installs
correctly.

Currently flake8 does not run succesfully so it is configured to not fail the
build on Travis.