Add support for requesting raw bytes.

People have their reasons. We're going to use the same `IHttpClient`
to request emoji images.

Octokit.Tests.Integration/HttpClientAdapterTests.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Linq;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+using Octokit.Internal;
+using Octokit.Tests.Integration;
+using Xunit;
+
+public class HttpClientAdapterTests
+{
+    public class TheSendAsyncMethod
+    {
+        [IntegrationTest]
+        public async Task CanDownloadImage()
+        {
+            var httpClient = new HttpClientAdapter();
+            var request = new Request
+            {
+                BaseAddress = new Uri("https://github.global.ssl.fastly.net/", UriKind.Absolute),
+                Endpoint = new Uri("/images/icons/emoji/poop.png?v=5", UriKind.RelativeOrAbsolute),
+                AllowAutoRedirect = true,
+                Method = HttpMethod.Get
+            };
+
+            var imageBytes = await httpClient.Send<byte[]>(request, CancellationToken.None);
+
+            // Spot check some of dem bytes.
+            Assert.Equal(137, imageBytes.BodyAsObject[0]);
+            Assert.Equal(80, imageBytes.BodyAsObject[1]);
+            Assert.Equal(78, imageBytes.BodyAsObject[2]);
+            Assert.Equal(130, imageBytes.BodyAsObject.Last());
+        }
+    }
+}