ENH: add distance gufuncs to `scipy.spatial`

This provides a new submodule `umath_distance` to `scipy.spatial`, that provides gufuncs for distance calculations. The Python wrapper to the C coded gufuncs allows `pdist` and `cdist` style calculations with a simpler, common interface.

Only functions of two inputs with no additional parameters are included in this version, i.e. everything provided in `scipy.spatial.distance` except `mahalanobis`, `minkowski`, `seuclidean` and `wminkowski`.
Removed non-ASCII characters from comments in umath_distance.c.src causing problems with Python 3.x builds
Merge branch 'umath_distance' of https://github.com/jaimefrio/scipy into umath_distance

Conflicts:
	scipy/spatial/src/umath_distance.c.src