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
```
Doesn't CI specify webdriver in a config instead of part of a gulp test? I think CI usually runs the test script specified in package.json also. I think this is just for devs.