Replaced Jasmine expect with unexpected

[sunesimonsen]

I think it would provide new users with better feedback if javascript-koans used unexpected instead of the build in expect from Jasmine. Unexpected is just better in all aspects than the Jasmine expect. It provides colored error messaged with helpful diffs. It is also has better documentation and many more features. See https://unexpectedjs.github.io for more information.

I know this is not the kind of pull request a project normally want, but I think unexpected would fit nicely with javascript-koans. There will be no hard feelings if you just reject the pull request, but I of cause hope you would consider it. That might also make me want to contribute further to the koans in the future.

Kind regards.