WCT v1.3.0

* Added more libraries to the default environment:
  * Sinon
  * sinon-chai
* The default environment can now be skipped (everything except mocha).
* When running tests via `wct`, `browser.js` and `environment.js` are
  served directly from WCT's copy rather than Bower. You no longer
  need to take a bower dependency on WCT if you only use `wct`!
* Introduced a `wct-st` tool that spins up a sauce tunnel.