Upgrade RestSharp and target .NET Framework 4.6.1#14

lindaps wants to merge 2 commits intotextmagic:mastertextmagic/textmagic-rest-csharp:masterfrom

lindaps:f/upgrade-dotNetFramework-and-RestSharplindaps/textmagic-rest-csharp:f/upgrade-dotNetFramework-and-RestSharpCopy head branch name to clipboard