lyrics: add musixmatch source
lyrics: add 'sources' option
lyrics: preserve default order of sources
move helper functions from utils to plugins
add a link to musixmatch.com
lyrics: update unit tests
remove test_util.py
remove print
lyrics: add 'force' option
Merge pull request #1150 from Kraymer/lyrics_force

lyrics: add 'force' option
lyrics: Connect force option to CLI (#1150)
Merge pull request #1148 from Kraymer/lyrics_musixmatch

lyrics: add 'musixmatch' source

Conflicts:
	beetsplug/lyrics.py
Privatize global SOURCES in lyrics
fetchart: Privatize global source list (#1148)
Changelog formatting (#1148)
fix lyrics.com extraction markers
fix black magic woman lyrics keywords

“sticks” is last word of sentence so can be spelled “sticks.”, “magic”
is less ambiguous.
fix lyrics.net song url
change lyrics.com song
add lyrics.com and lyrics.wikia.com to google srcs