slightly speed up matrix operations by avoiding isinstance
slightly speed up matrix operations by avoiding isinstance

a = randmatrix(30,30)

before:
>>> timing(a.__mul__, a)
0.28387993446094401

after:
>>> timing(a.__mul__, a)
0.25270753685175068

bjodah/mpmath,klkuhlm/mpmath,JensGrabner/mpmath,klkuhlm/mpmath,JensGrabner/mpmath,fredrik-johansson/mpmath,bjodah/mpmath