Add missing limit parameter for track.getSimilar

[redshodan]

Fixes #249

Changes proposed in this pull request:

• Add the limit parameter to the track.getSimilar query

[redshodan]

The build failed with "Invalid API key - You must be granted a valid key by last.fm". I guess something needs updating?

[hugovk]

See #171 for why it failed. I'll test locally.

Please could you add unit tests? Something like

pylast/tests/test_pylast_user.py

Lines 136 to 145 in e0f52ac

	def test_love_limits(self):
	# Arrange
	# Currently test-account has at least 23 loved tracks:
	user = self.network.get_user("test-user")
	# Act/Assert
	self.assertEqual(len(user.get_loved_tracks(limit=20)), 20)
	self.assertLessEqual(len(user.get_loved_tracks(limit=100)), 100)
	self.assertGreaterEqual(len(user.get_loved_tracks(limit=None)), 23)
	self.assertGreaterEqual(len(user.get_loved_tracks(limit=0)), 23)

[redshodan]

Added. That worked for me, however these two other tests failed. I'm wasn't terribly sure what to put for the lower limit of the tests with no limit, but 23 worked for this Cher song.

TestPyLastAlbum.test_album_in_artist_tracks
TestPyLastUser.test_album_tracks

[hugovk]

Thanks, merging!

test_album_in_artist_tracks passes for me, but test_album_tracks also fails on master, so I'll sort those later.