initial commit for the elm logger

A basic implementation of ELM, a wannabe ELMAH. Currently the logs are written to a dictionary and are displayed in plain text

![elmloggerinitial](https://cloud.githubusercontent.com/assets/2818455/4650805/c8578f66-5496-11e4-9e85-dc8d51da1d1a.png)

Throwing an exception here will make MVC unusable as it relies on `BeginScope` for its route handler and the default action selector.

If you don't wanna implement it yet, I'd suggest returning either `null` or a dummy `IDisposable` (returning `null` shouldn't be an issue given that `BeginScope` is only used with `using`, but a custom `IDisposable` is probably better).