Add minClientVersion 4.0.0, used by vs2017 (#84)

Author: matthias-hoste

NuGet/cef.redist.win.nuspec

@@ -1,6 +1,6 @@
 <?xml version="1.0"?>
 <package xmlns="http://schemas.microsoft.com/packaging/2010/07/nuspec.xsd">
-  <metadata>
+  <metadata minClientVersion="4.0.0">
     <id>cef.redist.win-$Platform$</id>
     <version>$version$</version>
     <authors>The Chromium Embedded Framework Authors</authors>