add phantomjs as dev dependency for karma

[simon-thorpe]

Added phantomjs as npm dependency. Without it I was getting:

26 01 2016 07:48:25.398:INFO [karma]: Karma v0.13.19 server started at http://localhost:9876/
26 01 2016 07:48:25.399:WARN [launcher]: Can not load "PhantomJS", it is not registered!
  Perhaps you are missing some plugin?

This error still occurred when phantomjs was installed through linux package manager and in path at /usr/bin/phantomjs

Also fix a typo in tests.js

[urish]

Thanks!