Fix broken JSON deserialization in .NET 4.5 (#1647)

* Cross target Octokit.Tests against netcoreapp1.0 and net452

* Add net45-specific references

This fixes a build error after adding the net452 target:
error CS0656: Missing compiler required member 'Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo.Create'

* Add SimpleJson conditional compilation symbols for net45

* Disable AppDomain when running tests

Thanks to Dominick and Patrik: https://twitter.com/leastprivilege/status/893376624233762816

* Use nameof operator instead of magic strings

* Remove conditional compilation symbols as they are not used in the conventions tests project

* Enable cross targetting in the conventions tests project

* Run tests against netcoreapp1.0 only when not on Windows

* Going too fast bites you

build/Context.cs

@@ -1,3 +1,6 @@
+using Cake.Common;
+using Cake.Common.Diagnostics;
+using Cake.Common.Tools.DotNetCore.Test;
 using Cake.Core;
 using Cake.Core.IO;
 using Cake.Frosting;
@@ -23,6 +26,26 @@ public class Context : FrostingContext
 
     public Project[] Projects { get; set; }
 
+    public DotNetCoreTestSettings GetTestSettings()
+    {
+        var settings = new DotNetCoreTestSettings
+        {
+            Configuration = Configuration,
+            NoBuild = true,
+            Verbose = false
+        };
+
+        if (!this.IsRunningOnWindows())
+        {
+            var testFramework = "netcoreapp1.0";
+
+            this.Information($"Running tests against {testFramework} only as we're not on Windows.");
+            settings.Framework = testFramework;
+        }
+
+        return settings;
+    }
+
     public Context(ICakeContext context)
         : base(context)
     {