Add a minimal build target

[jonnor]

Would go up on noflojs.org/noflo-browser next to everything.js/html

Could be used for quick&easy deployment scenarios. Would need to make sure that there is a way to inject custom component libraries without doing a rebuild though.

[bergie]

We might be able to use webpack externals for modularizing the whole build, actually:

http://webpack.github.io/docs/library-and-externals.html