Fixes #2676 : Convert Matrix to NumPy Array with NumPy dtype

Exposes dtype to the user. Default dtype is 'object'.
Rename d_type to dtype
Added tests for matrix2numpy
Merge branch 'patch-1' of https://github.com/venkateshhalli/sympy into venkateshhalli-patch-1

Conflicts:
	sympy/external/tests/test_numpy.py
Merge pull request #7446 from certik/venkateshhalli-patch-1

Fixes #2676 : Convert Matrix to NumPy Array with NumPy dtype