Async all the requests!
The big one, touching a  lot of files. Checkpoint commit not that it compiles
- Please() and Response() return Task<T> not T. All requests are async
- using System.Net.Http.HttpClient (new in .Net 4.5) for the underlying Http connection. It's better in many ways. and it's only async.
- all tests are async and await.
- Delete the HttpMethod enum as .net 4.5 has this (though each http method is now an object not an enum member)
Fix tests
Notably that HttpMethod is not an enum any more (see System.Net.Http.HttpMethod),
and HttpMethod is not serializable, when it needs to be in a request in an exception
but these can be worked around
Merge pull request #162 from AnthonySteele/dot-net-45

Dot net 45