Added a How-To for OSX for issue #28
Minor How-To improvements. Added a link to releases.
Added a donation button.
Use a smaller, english donation button
Even smaller :-)
Fixed a problem of the "On Google Music" track info menu

When title or artist where missing the "On Google Music" track
info menu where not build up correctly. Better check if $title
and/or $artist are available.
Merge branch 'v0.3' into feature/SmartMix