Changed travis to use conda
Exclude certain configurations from travis as bin packages are not available.
Restored Python 3.2 testing in travis (without NumPy)
Added wheel configuration to setup.cfg
Fix issue #156, SI prefix error on ureg.convert
Changed travis config to use mwcraig channel supporting 3.2
Added extra NumPy python versions to Python 3.2
Merge branch 'master' of git://github.com/jdreaver/pint
Renamed "to_delta" to "as_delta" to stress that it's an interpretation but no conversion

Code, tests and documentation were updated.
Solve conflicts in CHANGES
Merge branch 'develop' into feature/_offset_units (conflicts manually resolved)