Remove specific version of json.net from being merged with ilmerge

Decouple Stripe.net from using a specific version of Json.NET via ilmerge.  Instead it's included as a package dependency.  This allows referencers to use newer versions of Json.NET via binding redirects in App.config or Web.config.  The problem this solves is StripeCharge objects failure to serialize properly using newer versions of Json.NET due to the included version being hard-coded (newer versions of Json.NET ignored the older versions of JsonProperyAttribute, etc.).

These commits remove the source-controller versions of package dependencies in favor of NuGet package restore.  Also, the packages.config files were out of sync with the actual versions referenced, so this was corrected.

I am unsure how to properly test the nuspec, any advice would be appreciated.