Reverted ivim.py to the master to separate the DTI and IVIM PRs
Reverted ivim.py to the master to separate the DTI and IVIM PRs

villalonreina/dipy,FrancoisRheaultUS/dipy,nilgoyyou/dipy,FrancoisRheaultUS/dipy,nilgoyyou/dipy,villalonreina/dipy