TST - added test for dipy_fit_tensor script
RF - have dipy_fit_tensor use TensorModel instead of Tensor
RF - Take dti.Tensor out of dipy in favor of dti.TensorModel
RF - use sum/mean in dipy.reconst.dti
Merge pull request #163 from MrBago/remove_dti_Tensor

Remove dti tensor
Calculation for mode of a tensor
Updated Tensor Mode calculation for n-dimensional array
Cleaned up tests and typos
Doc reference fixes
RF: Rewrite of the tensor mode calculation with no loops.

Also, broke it down into separate functions, added some testing, etc.
Latex squiggle on A for Tensor Mode docs
DOCS + PEP8
RF: got the terms mixed up a bit.
RF: Rebased from master