BUG: Campanion Matrix was scalar, not matrix for degree 1.

The companion matrices returned by the various polynomial types was
a scalar in the degree one case instead of a 2-D array. Fix that and
add a test to check for that result.

Closes #3459.
Merge pull request #3460 from charris/fix-polynomial-companion-matrices

BUG: Campanion Matrix was scalar, not matrix for degree 1.