Add a lyrics backend that scraps results from google custom search api.

Add a 'fallback' option to facilitate working around the 100 queries/day google
limit by marking files as 'visited' so they are not considered for lyrics search
on the next beet run.
I've put my own google_engine_ID as default value in the code but could be
reconsidered, this engine contains databases known to be scrappable by the
plugin algorithm though.
lyrics: restore tags write and fix extract_text()
Code style + fix doc typo
Merge pull request #243 from KraYmer/master

Add a lyrics backend that scrapes results from google custom search api
misc. style cleanup for #243
docs and changelog for #243

Also note that this fixes #162.
Update lyrics.rst

fix typo
another docs typo
lastgenre: force real lookup during import only if no custom whitelist set.
sort Album.items() output

This closes #181 and #255, which fixed the problem in one usage (importfeeds).
Revert "lastgenre: force real lookup during import only if no custom whitelist set."

This reverts commit 4be30fca2e08d63eb4bfc21f7704fb95e5ef4d26.
lastgenre: invert 'force' option default value.
Merge pull request #254 from KraYmer/lastgenre-skip

lastgenre: force real lookup during import only if no custom whitelist set
changelog for #254
smartplaylist: split query w/ shlex (fixes #256)