add available element to locker response
remove locker test
Merge pull request #159 from danbadge/master

Add available element to locker response
Have updated this test as the behaviour being tested is no longer valid, having been removed from the artist/toptracks endpoint. The new functionality is to just return an empty result set rather than a 1003 error
Merge pull request #160 from gregsochanik/toptracks-test-update

Toptracks test update