Make `Angle` a subclass of `Quantity`.
Python 3.x fixes
Use np.vectorize rather than np.nditer, for Numpy 1.5 support
Fix bounds checking.  Operations succeed if the bounds are default on one of the operands, as long as the result is within bounds.
Fix path.
Fix bug in Angle("3d")
Minor docstring fixes
Fix problems parsing sequences of strings
Include unit in out of bounds message
Support `Angle.dms` on arrays.
Remove accidental change in the return type of `Angle.to_string`
Fix dms and hms to return a tuple of arrays -- this allows for round-tripping.
Fix crash in Angle.to_string() with a composite unit
Fix error on Numpy 1.5
Merge pull request #1006 from mdboom/unit/quantity-subclasses

Make `Angle` a `Quantity` subclass