XmlDeserializer.HandleListDerivative does not try the lowercased, "undashed" version for element names.

Issue was reported here:
http://groups.google.com/group/restsharp/browse_thread/thread/c70c39b47d10002d
Fixed an issue regarding Silverlight and Windows Phone clients weren't sending Cookies on request
Propagate connect failures et al. upwards to avoid crashing later with a nullref in Http.ExtractResponseData
Changed string comparisons to use `OrdinalIgnoreCase` rather than `InvariantCultureIgnoreCase`.

Not only is ordinal comparisons faster since it does a byte by byte comparison, but for the case of dealing with HTTP headers, it's also the more correct comparsion to do as of .NET 2.0 (see the [MSDN recommendations for string comparisons](http://msdn.microsoft.com/en-us/library/ms973919.aspx)).

As an example, try running these two lines of code:

    Console.Write(String.Equals("Password", "Paßword", StringComparison.OrdinalIgnoreCase));
    Console.Write(String.Equals("Password", "Paßword", StringComparison.InvariantCultureIgnoreCase));

Notice the first (ordinal) comparison returns `false` and the second (invariant culture) returns `true`.
Implemented `ExecuteAsync` overload as an extension method of `IRestClient`.

The concrete implementation `RestClient` has a nice `ExecuteAsync` method that's simply a wrapper to a call of another method on `IRestClient`. Since this method can be completely implemented in terms of the `IRestClient` interface, it makes sense to make it an extension method of `IRestClient`. The benefit is that I don't need to pass around a `RestClient` in my own API but I can pass around an `IRestClient`. Makes unit testing easier too, and that comes for free! Added bonus! :)
Another extension method
Merge pull request #219 from Haacked/stringcomparisonfix

Changed string comparisons to use `OrdinalIgnoreCase`
Merge branch 'restclientextensions' of https://github.com/Haacked/RestSharp into Haacked-restclientextensions
adding haack's restclientextensions to WP/SL projects
bump to 102.7 with json.net 4.0.8, now with less strong naming for WP/SL. hooray :)
use framework string decoding for non-SL versions (thanks @tt)
including XML doc files in download
Fixed bug that errors in http communication are not propagated correctly if response is empty.
Merge branch 'master' of github.com:restsharp/RestSharp
Merge pull request #215 from PedroLamas/master

Made Silverlight and Windows Phone clients send Cookies on request
Fix typo in RestClient.CookieContainer documentation.
"No bug left behind."
Merge pull request #226 from aaronlerch/patch-1

Fix typo in RestClient.CookieContainer documentation.
Edited the IRestClient to have the execute functions return IRestResponse
instead of the derived type to allow for more natural mocking without
having to cast the mock object and added an extension method for
converting responses to generic reponses

 	modified:   RestSharp/Deserializers/DotNetXmlDeserializer.cs
 	modified:   RestSharp/Deserializers/IDeserializer.cs
 	modified:   RestSharp/Deserializers/JsonDeserializer.cs
 	modified:   RestSharp/Deserializers/XmlAttributeDeserializer.cs
 	modified:   RestSharp/Deserializers/XmlDeserializer.cs
 	new file:   RestSharp/Extensions/ResponseExtensions.cs
 	modified:   RestSharp/IRestClient.cs
 	modified:   RestSharp/RestClient.Async.cs
 	modified:   RestSharp/RestClient.Sync.cs
 	modified:   RestSharp/RestClient.cs
 	modified:   RestSharp/RestClientExtensions.cs
 	modified:   RestSharp/RestResponse.cs
 	modified:   RestSharp/RestSharp.csproj
Extended JsonDeserializer to add support for TimeSpan incl. UnitTests.
Supported format is: "00:00:00.0000000"
Added UnitTest data for TimeSpan