BUILD: use numpy-wheels/openblas_support.py to create _distributor_init.py

* DOC: Change "random" to "uninitialized" in doctests 

ENH: randomgen

This merges randomgen into numpy, which was originally developed at https://github.com/bashtage/randomgen and provides a new and improved API for random number generation with much new and improved functionality.

* bump OpenBLAS version to 0.3.7.dev
in Azure CI to pick up AVX512 SkylakeX
fixes and match wheels

* use ctypes code to verify appropriate
version of OpenBLAS

first cut at building randomgen
upgrade 'cythonize' and fix absolute imports to relative
define NPY_NO_DEPRECATED_API and fix other warnings
enable pgc64 by always using PCG_EMULATED_MATH
refactor so import randomgen works
add TODO comments for pcg64 improvements
fix imports, module name in setup.py; remove _testing
make cythonize non-recursive, restore examples to proper place
update to randomgen 7bca296c0b9
replace mtrand with LegacyGenerator, tweak for compatibility
port f879ef4 to fix GH10839
minimized difference between generator.pyx and _legacy.pyx
fix namespace in doctests, mark results that are random
update to randomgen commit 95c8cdd1c
Incorporate testing of edge cases into main tests
Rename test files to describe their purpose
Import import locations to reflect numpy paths
Correct tolerance on float32 tests
Remove set_printoptions
Remove complex normal
Remove future imports
Pull in BasicRNG source changes from original author
Small doc fixes
_mtrand => _rand
Improve consistency of nan handling
Prevent nans prducing values from int functions
add randomgen documentation to the tree

* Travis CI will now fail NumPy builds
at the compilation stage when
implicit-function-declaration is detected;
otherwise, C functions without included prototypes
may be allowed to pass through with a warning

See https://docs.python.org/2/library/unittest.html#deprecated-aliases