Stable node.js now runs contracts.coffee!

Took almost a year but now the stable version of node.js (0.8.0+) has a recent enough version of V8 to run contracts.coffee! The much needed proxy support is still behind a flag so you'll need to supply harmony proxies and harmony collections as usual. Also, the latest version of contracts.coffee (0.3.1) and is now up on npm and collects a few bugs fixes.