title: get all types in assembly with custom attribute
body: <p>Is there an elegant way to get all the types in an assembly that have a custom attribute?</p>
  
  <p>So if I have a class</p>
  
  <pre><code>[Findable]
  public class MyFindableClass
  {}
  </code></pre>
  
  <p>I would like to be able to find it in a collection of types returned by Assembly.GetTypes(...)</p>
  
  <p>I can do it with a big vile hack, but I'm sure someone has a nicer way.</p>