latest self host lib to prevent error

When I cloned this and ran the self host I instantly got the error 

`Error: System.TypeLoadException: Inheritance security rules violated by type: 'System.Web.Http.SelfHost.HttpSelfHostConfiguration'. Derived types must either match the security accessibility of the base type or be less accessible. `

Did a quick Google and came across [this](https://aspnetwebstack.codeplex.com/workitem/1646), so I updated the libs and it worked fine after that.