Added min_weight option to lastgenre, to provide for filtering out unpopulare genres.
The following only applies when ```multiple``` is activated:
Return one valid genre even if its weight is lower then ```min_weight```.
Default for ```min_weight``` is now *10*.
Added new config option ```max_genres``` to limit the amount of genres returned.  Default is *3*.
Workaround for pylast issue https://code.google.com/p/pylast/issues/detail?id=85 as suggested by @sampsyo
Bugfix for Album.get_top_tracks workaround.
The way of the impatient is filled with useless commits :(
fixed indentation
Merged the ```multiple``` and ```max_genres``` option into one ```count``` option.
Updated debug output to waste less lines.
make the doc 'clearer'
Merge pull request #416 from pscn/master

Added min_weight option to lastgenre plugin, to provide for filtering out unpopular genres.