Better FactoryGirl syntax

Mixing in the FactoryGirl syntax so that you can call create/build/etc. on their own is (to me) harder to understand, coming into the project, than invoking those methods on the FactoryGirl class. Since we want to make this project as accessible to other developers as possible, I think it's better to be explicit about this.

Note: this will have the same spec failures as master, #145 resolves those.