Wrong variable name in return statement.
Add a Makefile for minifying the code.

It uses the Google Closure Compiler, from here:
https://developers.google.com/closure/compiler/

There's also a target for producing a single un-minified file from all
the sources. It just cats them together, but hey, it works.
Fix trailing comma issues reported by the Closure Compiler.
Add the build directory to the .gitignore
Update the README