Don't hardcode IE polyfills in header.php

[tobeycodes]

As discussed in #9 we will need to at least add https://github.com/keithclark/selectivizr and most likely some other changes to support older browsers

[tobeycodes]

We should enqueue any IE conditional stuff with instead of directly in header.php

https://developer.wordpress.org/reference/functions/wp_script_add_data/

[frankiejarrett]

Agreed. It's now a requirement on dot org: https://make.wordpress.org/themes/2016/07/26/meeting-notes-for-2016-july-26/

[jonathanbardo]

This is now resolve since we merged the susy branch.