RF - Cleaned up dti.py, eigen decomposition of tensor implemented as cache, and renamed functions to reflect the general utility such as eig_decomp
RF - Cleaned up dti.py, eigen decomposition of tensor implemented as cache, and renamed functions to reflect the general utility such as eig_decomp

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