Gruntfile: Added open target for coverage directory.

Hardcoded PhantomJS 1.9.7 (Mac OS X) folder name may suck in the future.
Karma: Advanced testing.

Multiple Karma configuration files to run tests on PhantomJS, Chrome, Firefox, Safari and even SauceLabs.
Tests: Fixed button test for Firefox.

Somehow Firefox requires button to be appended to document. It's interesting that it's working fine for other tests. It seems there is a glitch with disable and dispatchEvent.