Fix AngleAxisToRotationMatrix near zero.

The Taylor series approximation had its sign flipped and the
tests did not catch it since we were switching exactly at zero,
which was not getting triggered.

This changes modifies the tolerance, adds a test that triggers
and fixes the bug.

Thanks to Michael Samples for reporting this.

Change-Id: I6f92f6348e5d4421ffe194fba92c04285449484c
2 files changed