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: isinf is not defined in visual C. Using cimport instead.
BF: using cimport from libc.math instead of math.h in vector_fields and expectmax
BF: compare the return value of isinf against zero. Apparently it is returning a python Boolean instead of a simple int (I don't have this problem on my side though, if this doesn't work we may need to acquire the gil)
BF: using numpy's isinf with gil. Apparently isinf is not defined in libc.math
BF: imports math.h functions via dpy_math.h