first work on removing target from landmarks
Merge remote-tracking branch 'upstream/master' into rmlmtarget

Conflicts:
	menpo/landmark/base.py
fix tests for landmark targets
tidy up imports
view_landmarks() via LandmarkableViewable
add LandmarkableViewable to the API refererence
Merge pull request #395 from jabooth/rmlmtarget

remove cyclic target reference from landmarks