Added CMS to prerelease NuGet config.

Author: AndyButland

NuGet.config

@@ -11,9 +11,11 @@
       <package pattern="*" />
     </packageSource>
     <packageSource key="Umbraco Prereleases">
+      <package pattern="Umbraco.Cms.*" />
       <package pattern="Umbraco.Deploy.*" />
     </packageSource>
     <packageSource key="Umbraco Nightly">
+      <package pattern="Umbraco.Cms.*" />
       <package pattern="Umbraco.Deploy.*" />
     </packageSource>
   </packageSourceMapping>