adapt to recent Gatherer changes

This pull request also adds Underscore as a dependency, which simplifies much of the code.

[Vanguard][1] cards no longer appear in Gatherer, so I disabled these tests.


[1]: http://gatherer.wizards.com/Pages/Search/Default.aspx?advanced=true&output=standard&page=0&set=%5B%22Vanguard%22%5D