reactstrap version 4.8.0

Issue description

I'm using the Collapse component for my .navmenu, in Bootstrap v4 alpha 6, the styling was good.
Now I've updated to v4-beta and this is the result:

As you can see the color of the .nav-link inside the collapse are more white. This is because of the .show class that is being used in v4-beta. The .show class is also used by reactstrap for the Collapse component which now messes with the styling.

You can see the class in the source here: https://github.com/twbs/bootstrap/blob/35f80bb12e4e71fd777ee60ffa43711d8f84b1a6/scss/_navbar.scss#L264