WIP: Started implementing cross-validation from model predictions.
ENH: A bit more work on cross-validation.
BF: The order of the output needs to be like the order of the data...

Also: some more flexibility on the model API that is accepted.
PEP8

Before I start mucking about here.
PEP8
PEP8
BF: Predict properly, by separating b0s and diffusion-weighted samples.
WIP: Work towards xval prediction in csdeconv.
DOC: optional arguments and their default values.
RF: Make this part of the reconst module, instead of its own thing.
RF + TST: Predict the signal from CSD model, check with kfold xval.
TST + DOC: Fixed test for csd xval, added reference for xvalidation on DWI.
RF: Removed some cruft.

This is related to prediction of DKI, which I leave for some other day.
PY3K
TST: as long as it runs...
Minor: this test is DTI-specific.
ENH: Generalize kfold xval to multi-voxel CSD.
Small one: PEP8.
TST: Adding a test for informative error with models that don't have `predict`
TST: Implementation of error raising for models with no `predict`.