Revert "only do special sorting of real roots"

This reverts commit 3a5529a3906c65f96f53056e46d0a4fa3f09a5c9.
Revert "roots_quadratic in polyroots.py: returns appropriately sorted roots"

This reverts commit 114a0dc9d2be9cd96925993c04b2fc7bf43fb46c.
only sort roots when needed
Merge pull request #3 from smichr/roots

sort roots where necessary