MAINT optimize machinalis.png, -9kB/42%
FIX update sklearn.__all__ to include all end-user submodules
FIX define CC and CXX for travis
FIX Windows CI: use prebuilt numpy / scipy
MAINT remove harmless, but useless, double call to csr_matrix

The input validation code will already have performed the conversion.
Calling this constructor on a CSR matrix doesn't actually copy, but
it's useless too.
MAINT use %r for better printing of regexps
ENH friendlier message for calling predict before fit on SVMs

Fixes #3601.
ENH Add 'axis' argument to sparsefuncs.mean_variance_axis
ENH improved CSC matrix handling in VarianceThreshold