Added support for compiling with Closure, fixed up Makefile so it uses file-based dependancies rather than target depdendancies.  Still uses UglifyJS by default.  Added documentation for Closure compilation method.
Minor Markdown syntax fixing.
Refs #381. Minor readme tweaks for closure vs uglifyjs.
Refs #381. Added changelog entries and added Michael Farrell to AUTHORS
Merge pull request #384 from wymeditor/issue_381

Tweaks for #381 Google Closure support