Fix crash in tests due to scipy 0.13 interface change in sparce matrix.

It used to support ndarray of 2 elements for idx, now it ask for a tuple.
Work around a bug in scipy.sparse.hstack
Work around the dtype bug in scipy.sparse.vstack as for hstack()
Merge pull request #1636 from nouiz/scipy_0.13

Scipy 0.13 (needed for the release)