fetchart (issue 459): use regex to detect valid image names + 'cautious' option for finer control of filename matching
Clarify fetchart docs, and a couple corrections

Reading the fetchart docs it was not clear to me that it would use _any_
image file found alongside your music files, even if the image file did
not have one of the five privileged names (cover, front, art, album,
folder).  I humbly propose these edits to the docs in an attempt to make
it more clear that, by default, any local image file will be used.

I also corrected '"album," _for_ "folder"' to '"album," _or_ "folder"',
and from reading the code I'm pretty sure that remote_priority needs to
be true, not false, in order to prefer remote sources.
Merge pull request #259 from dsedivec/master

Clarify fetchart docs, and a couple corrections
fix link to MusicBrainz albumtype docs
Use re.search instead of re.match with simplified regex.
Add additional cover_names parameter to art_in_path, and makes 'cover_names' a  plugin config option.
Fix unit tests by constructing a FetchArtPlugin in the
fixture and using 'art.jpg' as default image filename so that 
'cautious' option does not interfere with the tests.
fetchart: document 'cautious' and 'cover_names' options
Merge branch 'fetchart-459' of git://github.com/KraYmer/beets

Conflicts:
	docs/plugins/fetchart.rst
API/test enhancements for #257

Also, `cautious` defaults to False for backwards-compatibility.
changelog for #257
Update fetchart.rst

fix option name and provided example
changelog summary
spell check
Added tag v1.1.0 for changeset 97f04ce25233
Merge branch 'master' of git://github.com/sampsyo/beets