BUG: use np.* instead of math.* to avoid problems with complex numbers
MAINT: add expm_multiply to scipy.linalg
MAINT: remove the expm_multiply from linalg because I am too noob at python to figure out the cyclic import issues
TST: add complex test
Merge pull request #2495 from argriffing/expm-multiply-maintenance

BUG: sparse.linalg: expm multiply maintenance