Fix comparison with None for artist, album and event, with test. For #97.
Last.fm returns no results for artist.getsimilar with limit=1, but limit=2 returns 2
Fix chart tests that failed due to date ranges
Fix chart tests that failed due to date ranges (take 2)
Merge remote-tracking branch 'upstream/master'

Conflicts:
	test_pylast.py
Badges! [CI skip]
Make test more robust
Merge remote-tracking branch 'upstream/master'
Use Docker
Merge pull request #107 from hugovk/master

Fix comparison with None; fix tests; use Docker; badges