popover should support a non atom showing?

[stumitchell]

currently popover-anchor-wrapper and popover-content-wrapper will generate an error if showing? is a value not an atom.

This code should be changed to allow a simple boolean value.

Stu

[Gregg8]

Would be happy to accept a PR for this ;-)

[stumitchell]

https://github.com/Day8/re-com/pull/153

[superstructor]

Fixed in 00e8645 as a result of #153