[V4 Beta 2] Outline button mouseover animation is jarring

Created by: mrlife

For a test case, the outline buttons in the docs exhibit the issue. It appears that the font color changes immediately, while the button color transitions. The effect is jarring when compared to the smooth/coordinated transition of V4 Beta 1. See: https://getbootstrap.com/docs/4.0/components/buttons/#outline-buttons

This is on macOS 10.13 and Safari 11.0.