Make JS invocation tag part of grunt build process

[alexanderdean]

Because currently it is handrolled and partially minifed. We should split into non-minified and minifed versions.

Let's keep the p, l, o, w, i, n, g if at all we can. I.e. it's better to keep that than create meaningful names for those 7 vars

[alexanderdean]

Done in 2.0.0, closing