Anton/videoalpha tests

Tests for VideAlpha player were added.
@cahrens , @shnayder: please review.

Notice: 
According to https://github.com/ariya/phantomjs/wiki/Supported-Web-Standards#unsupported-features Video and Audio (due to the nature of PhantomJS) are not supported. After discussion with William Daly, some tests are disabled in the last commit (Jenkins uses phantomjs for running tests and those tests fail).

During code review, please enable those tests and run them manually via "rake jasmine:common/lib/xmodule:browser". You should verify that all tests pass.