Development toolchain updates + OpenSauce

This introduces a `grunt server` development server that hosts jasmine (with automatic spec runner generation and updating) at http://localhost:8888/spec.

This also introduces OpenSauce, which will let us test dc.js on many different browser configurations. We're currently failing tests in Safari and IE, so I'll fix those before merging this in. It also seems like OpenSauce can't handle the test suite object we're passing to their server (or my port of JSReporter to jasmine 2 is broken), so the OpenSauce output is just pass/fail for now and requires viewing the screencast to see the failed specs.

Thoughts?