Migrate from Shared Caching to Windows Azure Cache Service

The current project uses the [Nuget package for Windows Azure Shared Caching](https://www.nuget.org/packages/WindowsAzure.Caching/). However, the [MSDN documentation](http://msdn.microsoft.com/en-us/library/windowsazure/gg278356.aspx#SharedCaching) says that service will soon be retired in favour of [the new Windows Azure Cache package](https://www.nuget.org/packages/Microsoft.WindowsAzure.Caching/). This pull request simply makes that migration.

I simply followed the instructions on the following page:

http://msdn.microsoft.com/en-us/library/windowsazure/dn386110.aspx