Menu remains displayed after clicking outside

[ed-bassett]

Steps to reproduce:

1. Select any panel on the left side
2. Press x to show the menu
3. Click on the panel on the right (left half of menu remains displayed over the panels on the left)

Desired behaviour:
Either menu is modal, and clicking outside should be disallowed or clicking outside is meant to close the menu, and should completely remove the menu from the screen.

[jesseduffield]

fixed in #43 (I'm just going to make it that you can't click out if you have a popup panel because it may be asking you something you need to answer to continue)