RF - Adding doc strings, writing methods, and reorganizing tensor class in dti.py
RF - Adding doc strings, writing methods, and reorganizing tensor class in dti.py

villalonreina/dipy,villalonreina/dipy,jyeatman/dipy,FrancoisRheaultUS/dipy,demianw/dipy,beni55/dipy,oesteban/dipy,jyeatman/dipy,rfdougherty/dipy,JohnGriffiths/dipy,nilgoyyou/dipy,demianw/dipy,maurozucchelli/dipy,nilgoyyou/dipy,maurozucchelli/dipy,beni55/dipy,FrancoisRheaultUS/dipy,mdesco/dipy,JohnGriffiths/dipy,maurozucchelli/dipy,matthieudumont/dipy,StongeEtienne/dipy,samuelstjean/dipy,samuelstjean/dipy,matthieudumont/dipy,StongeEtienne/dipy,samuelstjean/dipy,Messaoud-Boudjada/dipy,mdesco/dipy,Messaoud-Boudjada/dipy,sinkpoint/dipy,oesteban/dipy,rfdougherty/dipy,sinkpoint/dipy