Minification issues

[oliverfoster]

Subject of the issue

adapt/js/adapt.min.js should be minified by uglifyjs
adapt/js/build.min.js shouldn't be minified by uglifyjs as it is json

es6 is currently not supported by a released version of grunt-contrib-uglifyjs
this means the javascript command doesn't minify the adapt.min.js file properly due to a let statement in the notify module

also remove ie8 support from uglifier

[brian-learningpool]

I think we should remove thelet statement to resolve this, and review and update the code for v4 (or a later version of v3) rather than introducing ES 6 piecemeal.

[oliverfoster]

cool, i'll have a look through the core bits as i go, any plugin containing es6 will break after i reinstate minification. so could be a bit of a hassle

[oliverfoster]

https://swizec.com/blog/fun-surprise-uglifyjs-cant-es6/swizec/7272

[moloko]

find it a bit depressing that we can't use the only two bits of ES6 that are actually supported in ALL current browsers but there you go, I guess there's little we can do.

[oliverfoster]

v5 I'm going for webpack. So we're not far.