Hook up text editor quicktags

[jasmussen]

[ellatrix]

That code is probably a decade old. :)

[ellatrix]

In Calypso: https://github.com/Automattic/wp-calypso/tree/master/client/post-editor/editor-html-toolbar

[afercia]

Since WordPress 4.8 is going to drop support for old IE, worth considering to update the QuickTags code which still supports old IEs selection methods. See relevant ticket on Trac, now outdated: https://core.trac.wordpress.org/ticket/31661