Improve performance of arithmetic on MultiVector pairs (#283)
Improve performance of arithmetic on MultiVector pairs (#283)

The previous code was optimized for `MultiVector <op> something_else`, incurring an expensive `isinstance(other, numbers.Number)` check.

This changes it to check `isinstance(other, MultiVector)` first, which is the case that is going to be most frequent.
arsenovic/clifford,arsenovic/clifford