Adding class methods to doppler wcs
made space change
added the fix for 0.4 style models
Merge pull request #89 from wkerzendorf/wcs/new_model_fix

Wcs/new model fix
Removing Log WCS, adding documentation
Adding tests, and fixing an assignment bug
Changing doppler WCS, and adding classmethod for iraf doppler factor
Removing iraf doppler factor and adding inverse method to doppler shift model
Changing the deisgn of doppler wcs
Shifting computation to from_doppler_factor class method, fixing tests
Merge pull request #87 from shaileshahuja/doppler-log-wcs

Adding Doppler, LOG and identity WCSes
Adding LOG and Doppler WCS for linear and log-linear readers
Adding support for linear reader and writer and adding test for for writer
Using composite models and the new design of MultispecIRAFCompositeWCS to implement reader for multispec format
Rebasing on top of the model framework, and updating readers and writers to use this framework