Using ExceptionDispatchInfo instead of ExceptionExtensions

Here is my first pull request to this project. Hope I did everything according to the contribution guidelines. I swapped out the ExceptionsExtensions with the ExceptionDispatchInfo. The ExceptionDispatchInfo should be mono compliant as seen here: 

https://github.com/mono/mono/blob/master/mcs/class/corlib/System.Runtime.ExceptionServices/ExceptionDispatchInfo.cs

Daniel