Use a Fitter class that makes it easier to fit sources one by one without re-reading models. Also use FitInfoFile to make it easier to handle the reading/writing of fit information.
Allow input for all functions to be also a FitInfo instance or a list of FitInfo
Handle different types of input for input fits in FitInfoFile
Fixed failure with Python 2
Added docs about object-oriented interface
Merge pull request #12 from astrofrog/fitter-class

Fitter class