Aper adding wcs and support for various input data

I think this one needs more work, but can be merge as is if you prefer:

- [x] support more input data types
- [x] add unit test
- [x] add/change documentation
- [x] support more input coordinate formats
- [x] return user input coordinates and pixelcoordinates in the result table

Future:
~~accept non pixel unit for radius etc. when the wcs is provided.~~ Moved to future feature list in #131

@bsipocz - ah you are absolutely correct. Maybe we can just raise an error for now if a unit is passed but already defined on the FITS header or quantity input? It would seem strange to convert the data on the fly to a different unit, right?