Added nuget.config for prerelease feed support.

Author: Justin Skiles

NuGet.config

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+  <packageSources>
+    <!--To inherit the global NuGet package sources remove the <clear/> line below -->
+    <clear />
+    <add key="NuGet.org (v3)" value="https://api.nuget.org/v3/index.json" />
+    <add key="MyGet.org" value="https://www.myget.org/F/babelshift-ci/api/v3/index.json" />
+  </packageSources>
+</configuration>