np.outer and np.multiply.outer produce wrong result

[hameerabbasi]

Describe the bug
The shape of the inputs np.outer and np.multiply.outer is incorrect.

To Reproduce

>>> import numpy as np, sparse
>>> s1 = sparse.random((2, 3), density=0.5)
>>> s2 = sparse.random((3, 2), density=0.5)
>>> sparse.outer(s1, s2).shape
(3, 2, 2, 3)
>>> np.outer(s1.todense(), s2.todense()).shape
(6, 6)
>>> np.multiply.outer(s1, s2).shape
(3, 2, 2, 3)
>>> np.multiply.outer(s1.todense(), s2.todense()).shape
(2, 3, 3, 2)

Expected behavior
The behavior should match NumPy.

System

• OS and version: macOS 10.15.4
• sparse version: '0.9.1+24.gf6b3465'
• NumPy version: '1.18.1'
• Numba version '0.49.1rc1'

Additional context
First noticed by @Prabhat-LIINES in #345. See: #345 (comment)

[hameerabbasi]

@Prabhat-LIINES if you pull from master this should be fixed.