Replace test setups with action attributes

[jonsequitur]

I've refactored many of the tests to have less verbose, more composable setups using the NUnit action attributes feature.

[wli3]

Much less code to write and tests are easier to read. I have a problem tho, when should I create a new attribute instead of write the test set up in the Setup()?

[jonsequitur]

If the setup is reusable across sets of tests and orthogonal to other setups, it seems like a good candidate for an attribute. The setups that are left are largely very specific to their test classes.