NancyFx/Nancy — pull request #1696 by albertjan (2014-09-22 10:05:57+00:00)
Title: Async before pipeline exception fix

An async `BeforePipeLineItem` that threw an exception never completed.

This resulted in a neverendingrequest:
```c#
public class AsyncBeforeModule : NancyModule
{
public AsyncBeforeModule()
{
Before.AddItemToStartOfPipeline(async (ctx, c) =>
{
await Task.Delay(1000);
throw new Exception("aaargg!!");
});

Get["/"] = _ => "Hoi";
}
}
```