Update react-overlays dependency

[cutterbl]

React-Overalys is out of date

Current React-Overlays dependency is 0.8.3

The issue here is that other projects, such as React-Bootstrap, point to React-Overlays as a solution for creating Modal Managers, to handle multiple modals on a screen. Developers may want to use React-Bootstrap modals for Event Create/Edit screens, and conflicting versions of the React-Overlays dependency would cause major issues, as implementations have changed.

What's the expected behavior?

A developer would be able to use the current version of React-Overlays without major conflict.

Solution:

I submitted PR #1301 to address this issue.