Some more improvements and what's next

I've made two more files PEP8 compatible and removed the paddedStr from three files as it was never used and instead you, correctly, used zfill.

I'm currently working on further PEP8-ification and trying to undestand the code in the process. I'm also looking into using [astropy](http://www.astropy.org/) as this will allow us to get rid of some of the code (in particular the gregorian to julian and v. v. stuff, but I imagine there could be more) *and* the PyFITS is apparently now merged into astropy. Are you OK with that?

Then there're tests — I'll write the base code and some of the tests, but it would be nice if you added your own for some of the more esoteric stuff, if possible.

Also, it seems that you actually *do* use spaces, not tabs, so I'll keep using those.

Matt

PS. please, if possible, test this commit. I think I tested it before, but now I'm getting "Must have at least two data images", but I think that's just a PEBKAC, I've had the same problem before and can't remember what I did wrong in the GUI.
And I gotta go to bed now...