Upgraded builds to use psake

PSake build script currently supports
- Build
- Test

Will support 
- Package
- NugetPackage[Deploy]

will be able to target multiple framework targets, ie 2.0, 3.5, 4.0 since I see some 4.0 specific pull requests pending.

Perhaps we create a branch in your Repo for this?  And you can get comfortable with it before committing to master