Faster and less Last.fm api calls: Weekly tracks

[nick1n]

Need to implement a method so that we can reduce the amount of calls it does to the api service, such as, use weekly stats, instead of recent tracks, but at the same time need to make sure the weekly stats don't get cut off, also need to use recent tracks for beginning and end of months for accurate monthly stats. Also, remember not to cache the most recent week/tracks because they can change.

I'm pretty sure weekly charts get cut off after 500 entries, which can happen, in which case, we dump that data, and use Recent Tracks for that week, and have it take much longer 😕

[nick1n]

Related to Issue #50

[nick1n]

Closing this issue because we can't use Weekly tracks, since it doesn't include album name.