Added local variance estimation
Added option to use full volume or only non zero voxels
Added tests
stuff
removed estimate_noise
Added estimate sigma
removed estimate sigma test
added estimate sigma test
corrected copy paste error in filename
removed scipy convolve import
Added scipy convolve import
fixed test import
Update test_noise_estimate.py
BF: fix link to npy_math function

Link against numpy static math library - see
https://github.com/numpy/numpy/blob/master/doc/source/reference/c-api.coremath.rst
HACK: work round windows npymath compiling

Numpy binaries built with mingw have ``libnpymath.a`` library to link
against, but VC needs ``npymath.lib``.  The mingw library may be
compatible with VC, so detect the problem, and copy the library to a
temporary location to link against.
BF: supposed fix for the gh-439, but still unable to reproduce OP.
This doesn't do it either: we need somewhere were start_params is OK, but then
RESTORE fails.
RF + TST: Removed some (unused? Definitely untested!) cruft. More test
coverage.
TST: Test that a sequence of sigmas also works.
BF: Set min_signal to 0.0001 so that we can deal with normalized signal.

See https://github.com/nipy/dipy/issues/451