Make grid_from_affine a private function.  Add some documentation.
Make grid_from_affine a private function.  Add some documentation.
arokem/nipy,bthirion/nipy,alexis-roche/nipy,alexis-roche/nipy,nipy/nireg,alexis-roche/nireg,alexis-roche/nipy,nipy/nireg,alexis-roche/register,arokem/nipy,alexis-roche/register,nipy/nipy-labs,arokem/nipy,alexis-roche/niseg,nipy/nipy-labs,alexis-roche/nipy,bthirion/nipy,alexis-roche/niseg,arokem/nipy,alexis-roche/register,bthirion/nipy,alexis-roche/nireg,bthirion/nipy