Creates constructors for all Models.Response.

Resolves https://github.com/octokit/octokit.net/issues/677.

Removes obscolete properties (gravatar).
Makes Models.Response properties all be protected (most were already).

Octokit/Models/Response/SearchCodeResult.cs

@@ -1,4 +1,5 @@
-using System.Diagnostics;
+using System.Collections.Generic;
+using System.Diagnostics;
 using Octokit.Internal;
 
 namespace Octokit
@@ -6,5 +7,11 @@ namespace Octokit
     [DebuggerDisplay("{DebuggerDisplay,nq}")]
     public class SearchCodeResult : SearchResult<SearchCode>
     {
+        public SearchCodeResult() { }
+
+        public SearchCodeResult(int totalCount, bool incompleteResults, IReadOnlyList<SearchCode> items)
+            : base(totalCount, incompleteResults, items)
+        {
+        }
     }
 }