Minimize surface area (part 1)

After seeing some usage patterns and experimenting with these myself, I decided that we probably want to remove the class level run method. I felt adding it initially may keep us tied to an interface paradigm that we might not ultimately want to support -- because it adds some complexity to have three styles in running experiments.

This MR is phase one of setting us up to minimize the experiment(:example) syntax, and ExampleExperiment.new syntax.

I call this minimizing the surface area that we'll ultimately probably need to somewhat continue to support for the life of the project. I didn't bother doing a deprecation on this method as we're well on our way to a breaking change release with 0.5.0.