Set compilation based only on VA
Rename compilations tag
Add NEWS.txt update.
Address Michael's comment
Use comma rather than space delimiters in preserve_tags
Use upgrade mechanism to upgrade saved tag list.
Support the Jaikoz 'artists' tag, with help from @night199uk and @zas
Support .m4v files.

http://chatlogs.musicbrainz.org/musicbrainz/2013/2013-12/2013-12-08.html#T12-42-40-561267
Merge branch 'master' of github.com:musicbrainz/picard into artists-tag
USER_AGENT_STRING -> CLIENT_STRING, and use ORG/APP_NAME to build.
Append platform infos to user-agent string.

Exemple of output:
MusicBrainz-Picard/1.2.0final0 (Linux-3.5.0-17-generic-x86_64-with-LinuxMint-14-nadia;CPython-2.7.3)
Merge pull request #189 from Freso/support-m4v

Support .m4v files.
PICARD-539: ensure we append preferred encoding to normalized locale

http://tickets.musicbrainz.org/browse/PICARD-539
Update NEWS.txt
Merge branch 'master' of github.com:musicbrainz/picard into artists-tag
Merge pull request #190 from zas/useragent

Append system info to user-agent string, and build it from constants
Merge pull request #191 from zas/PICARD-539

PICARD-539: ensure we append preferred encoding to normalized locale
Indentation and spacing fixes, according to PEP8
Merge pull request #193 from zas/pep8

Indentation and spacing fixes, according to PEP8, only cosmetic changes.
Fix code formatting