Commented Task: Migrate Version 0.9 to target .NET Framework 4.0 [1965]

For testing purposes, Tweetinvi 0.9 was target 4.5 and should be available for .NET 4.0.
Consequently and for further development, the target of development should be 4.0.
Comments: Associated with changeset 34079: Version 0.9.0.0
- Removed dependency to Microsoft.Practices.Prism