Positioning issue in 0.4.18 (reproduced from 0.4.5 version)

[iJoyCode]

Hello, currently from 0.4.5 version of your library there is a wrong positioning. You can see it right on your storybook: https://littlebits.github.io/react-popover if you disable an animation. On click arrow first arrives at wrong place and then after a little moves to right place.

Please fix it.

[guyyt]

I'm having the same problem