Gulp task to run protractor tests

Gulp task to start `protractor` tests. Before running tests it ensures webdriver is installed (`ensure_webdriver_standalone`) and starts it (`webdriver_standalone`).

Usage:
```
gulp test
```
I personally don't like the "keep webdriver running indefinitely" model.  I think it's better use the "seleniumServerJar" option to have gulp-protractor manage the process for us