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
```
`webdriver_standalone` task needs to be started before `test` task. 1 second is enough to start it.
The other option is to parse `webdriver_standalone` console output and then call a callback function to start a next task but implementing this would take much more time. Since it's only be used by developers I thinks it's a better option.