OK - I have discovered that this entails that you can no longer initialize an OdfModel object without a gtab and an OdfFit object with data. This seems like a feature of the inheritance to me, rather than a bug, but I thought I would flag this. 

See: https://github.com/arokem/dipy/commit/4fecbc451af58b5fff0a1a7c14ea44c66fcd03a2