Replace binaries with content found in:
http://www.nuget.org/packages/NUnit.Runners/2.6.2
http://www.nuget.org/packages/NUnit.Runners/2.6.3

Was unable to get myget test runner working with existing binaries. It throws
a cryptic exception: System.ArgumentException: NUnit components for version 4.0.30319 of the CLR are not installed
Parameter name: targetRuntime