Removed reference to unexistant module

Hi,

I had forked your project about one year ago when it was not on Github. I can't wait to contribute to this project.

For now, this is a small correction for a reference to an unexistant module (princeton). And there is a file rename too pyspec.ccd.PrincetonSPE -> pyspec.ccd.files

I'll summit other things soon.

Regards,