Move to StyleCop.MSBuild v5.0.0

- stable release
- part of #65

Author: dougbu

.nuget/packages.config

@@ -2,6 +2,6 @@
 <packages>
   <package id="Microsoft.Web.SkipStrongNames" version="1.0.0" />
   <package id="Microsoft.Web.StyleCop" version="1.0.0" />
-  <package id="StyleCop" version="4.7.10.0" />
+  <package id="StyleCop" version="5.0.0" />
   <package id="xunit.runner.msbuild" version="2.2.0-beta2-build3300" targetFramework="net45" />
 </packages>