Updated Makefile for Uglify2, npm ignore, Mac OSX + perf notes.

Thanks for your work on this lib.. nice way to deal with JS prototypes. Here are a couple housekeeping edits I made for npm + uglify.

1. Vim undo files `*.un~` should now be ignored by npm.

2. I noticed that your uglify options were outdated since you're using the edge version in your pacakge.json. These new Makefile edits should update the uglify usage to v2.

3. Makefile is working fine on OSX (we're on GNU Make 3.81 now). Tests are passing, although I'm not sure if they were ran against the .min files.

4. For giggles, I created a jsperf test for P.js. Here: http://jsperf.com/oop-native-vs-pjs