Phantomjs testing

This pull adds a phantomjs unit testing framework, which was surprisingly easy thanks to @ronichoudhury's work in Tangelo.  Test cases are globbed from `testing/test-cases/phantomjs-tests/`.  Also included here are:
 * blanketjs coverage report that can be run at `/test/js-coverage/geojs-coverage.html` after starting an HTTP server from `deploy/`
 * automated travis testing, which I turned on at my [fork](https://github.com/jbeezley/geojs) along with a shiny "build passing" badge