Scan an assembly in order to create a DataContractContentSerializer

Resolves #100.
Let's take it in a different direction. I find the test difficult to read because, by looking at it, it's not clear to me *what* is being tested.

Normally, I look for a `sut` variable, and if I find one, I look for a [single, isolated line of code that exercises it](http://blog.ploeh.dk/2013/06/24/a-heuristic-for-formatting-code-according-to-the-aaa-pattern). However, here, the `sut` variable is only created *after* the behaviour that the test is exercising has been invoked, and I find that confusing.

The System Under Test is the system being *exercised* by the test. What is being exercised here?