Rotation labels

Add some map rotation knowledge in label renderer.
Horizontal and parallel line labels are now drawn correctly.
Curved labels are still suffering and I hadn't tested backshadow and such.

\cc @dakcarto for review

Related hub ticket: http://hub.qgis.org/issues/11814
No, the last 3 commits are just expeirments for travis, if you really want to see the real changes drop the last 3 (or even 4) commits. Will make this branch back to its original and focus on augmenting test tolerance tomorrow, if you leave some notes here about how to do that.