Merge pull request #9 from GaelVaroquaux/neighbors_np_1_3

COMPAT: empty_like does not have a dtype in np 1.3
COMPAT: make NeighborsHeap compatible with numpy 1.3
COMPAT: make NodeHeap compatible with numpy 1.3
COMPAT: make BinaryTree class compatible with numpy 1.3
COMPAT: make BallTree & KDTree compatible with numpy 1.3
COMPAT: last few BallTree/KDTree numpy 1.3 issues
COMPAT: fix arpack and pls on old scipy/numpy