http://blog.maartenballiauw.be/post/2013/05/28/Throttling-ASPNET-Web-API-calls.aspx
https://github.com/WebApiContrib/WebAPIContrib/blob/master/src/WebApiContrib/Caching/InMemoryThrottleStore.cs
https://github.com/WebApiContrib/WebAPIContrib/blob/master/src/WebApiContrib/MessageHandlers/ThrottlingHandler.cs
