Add ability to stop starring a repository

Change the `DeleteAsync` method to return `Task<IResponse<object>>` in
order to check the status code

Octokit/Clients/StarredClient.cs

@@ -116,5 +116,27 @@ namespace Octokit
                 return false;
             }
         }
+
+        public async Task<bool> RemoveStarFromRepo(string owner, string repo)
+        {
+            Ensure.ArgumentNotNullOrEmptyString(owner, "owner");
+            Ensure.ArgumentNotNull(repo, "repo");
+
+            try
+            {
+                var response = await Connection.DeleteAsync(ApiUrls.Starred(owner, repo))
+                                               .ConfigureAwait(false);
+
+                if (response.StatusCode != HttpStatusCode.NotFound && response.StatusCode != HttpStatusCode.NoContent)
+                {
+                    throw new ApiException("Invalid Status Code returned. Expected a 204 or a 404", response.StatusCode);
+                }
+                return response.StatusCode == HttpStatusCode.NoContent;
+            }
+            catch (NotFoundException)
+            {
+                return false ;
+            }
+        }
     }
 }

Octokit/Http/Connection.cs

@@ -205,7 +205,7 @@ namespace Octokit
             return Run<T>(request);
         }
 
-        public Task DeleteAsync(Uri uri)
+        public Task<IResponse<object>> DeleteAsync(Uri uri)
         {
             Ensure.ArgumentNotNull(uri, "uri");
 

Octokit/Http/IConnection.cs

@@ -13,7 +13,7 @@ namespace Octokit
         Task<IResponse<T>> PutAsync<T>(Uri uri, object body);
         Task<IResponse<T>> PutAsync<T>(Uri uri, object body, string twoFactorAuthenticationCode);
 
-        Task DeleteAsync(Uri uri);
+        Task<IResponse<object>> DeleteAsync(Uri uri);
 
         Uri BaseAddress { get; }