DOC: Add NEP and documentation for ufunc overrides.
ENH: Add ufunc override API.
ENH: Add ufunc override functionality to ufuncs and dots.
TST: Add ufunc override tests.
WIP: Added ufunc_override.h to setup.py.
BLD TRAVIS: Added libatlas to travis build so it can test BLAS stuff.

sudo apt-get install -qq libatlas-dev libatlas-base-dev