Disallow autoeye.__rmatmul__ for 1d arrays
Disallow autoeye.__rmatmul__ for 1d arrays

NumPy has the following behavior:

>>> (np.array([1, 2]) @ np.eye(2)).shape
(2,)
>>> (np.eye(2) @ np.array([1, 2])).shape
(2,)

That is, it treats 1d arrays as column or row vectors, depending on what side
you multiply. Since we want to treat them as column vectors, we disallow
__rmatmul__.  We should perhaps disallow __matmul__ as well, and require 2d
arrays in all cases.

ergs/transmutagen,ergs/transmutagen