Fix test filtering so that individual tests can be run

Addresses #31. Here's the result of running `ConstructorAndMethodTest`'s `single(Snack)` method:

![tests](https://cloud.githubusercontent.com/assets/828366/4672524/1527a718-5591-11e4-93da-eac1564a5adb.png)

Exceptions for control flow... is there's a giant middle finger emoji that I can point at JUnit?