Neighbors segfault fix

addresses #2190 

it sets wraparound=True in the cython header

I've also replaced ``X.shape[-1]`` with ``X.shape[X.ndim - 1]`` .
I haven't done it for  ``X.shape[:-1]`` though - if we do that than we can set wraparound=False again (at least I think so).

compiled kd tree and ball tree with cython 0.19.1