ESC key should exit pop-ups

[nwisehart]

Steps to reproduce:

• go to /a11y-map/index.html
• navigate area to pop-up
• open pop-up
• press 'esc'

Expected Behavior:

• should close the pop-up

Supporting Info:

• Google Chrome Version 68.0.3440.106
• OS X High Sierra
• localhost..././a11y-map/index.html

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See original at: https://github.com/kellyhutchins/a11y-map/issues/14

[nwisehart]

Look to 522a58e for solution