touch_ios7 no longer forces device rotation if orientation is
'unknown'.  instead it assumes a 'down' orientation when translating
the touch coordinates.

notes:

* device_orientation() will return "unknown" if and only if
  - running on the simulator
  - the simulator has not been rotated since the app was launched
Merge pull request #223 from jmoody/0.9.x-touch_ios7-should-not-force-an-orientation

0.9.x touch_ios7 should not force an orientation when orientation is 'unknown'