Changing aperture photometry output to return astropy.table

This is the first draft for returning the photometry results in an ``astropy.table``.
I think the main question is what we want to return. Only flux, fluxerr, or something more, e.g. positions, or even the apertures (as metadata), etc.  

It should be
```
`~astropy.table.Table`
```
instead of
```
`~astropy.Table`
```
I guess we need to turn `nitpicky` mode on to catch such things on travis-ci? Possible?