ES6 not supported in older browsers

[mi-lee]

See https://github.com/edgi-govdata-archiving/eot-nomination-tool/blob/master/popup.js#L3

I'm getting emails from a user with an older version of chrome.

[atesgoral]

Maybe just adding a 'use strict'; at the top of the file could resolve the above issue.

Beyond ES6, I'm now worried about my use of CSS flexbox...

[mi-lee]

Errr.... yeah, we shouldn't be using flexbox. Accessibility >>> convenience for a tool like this

[mi-lee]

use strict would solve that particular user's issue but given the tiny scope of this project and need for accessibility I'm opting to just go for the added minor inconvenience of switching to ES5

[atesgoral]

Fixed by #67