you can now "minify" javscript files with make js

Currently you have to copy/paste code to mailpile-min.js; this patch automates that.
It copies mailpile.js to mailpile-min.js and appends all javascript files located in static/default/js.

If you are interested in this patch I also offer moving comments from mailpile-min.js to respective non-minfied files and whitespace cleanup.