Docs: Separate Tether out from docs.min.js

Created by: cvrebert

We can't include it in docs.min.js because docs.min.js includes application.js, application.js depends on bootstrap.js, and the tooltip portion of bootstrap.js depends on Tether.

So instead, we need to load Tether separately before bootstrap.js

CC: @XhmikosR @hnrch02

added docs js v4 labels

changed milestone to %v4.0.0-alpha.2

closed