Rename com.squareup.okhttp to okhttp3

Maven group changes will come in follow up.

samples/guide/src/main/java/okhttp3/recipes/PostFile.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright (C) 2014 Square, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package okhttp3.recipes;
+
+import okhttp3.MediaType;
+import okhttp3.OkHttpClient;
+import okhttp3.Request;
+import okhttp3.RequestBody;
+import okhttp3.Response;
+import java.io.File;
+import java.io.IOException;
+
+public final class PostFile {
+  public static final MediaType MEDIA_TYPE_MARKDOWN
+      = MediaType.parse("text/x-markdown; charset=utf-8");
+
+  private final OkHttpClient client = new OkHttpClient();
+
+  public void run() throws Exception {
+    File file = new File("README.md");
+
+    Request request = new Request.Builder()
+        .url("https://api.github.com/markdown/raw")
+        .post(RequestBody.create(MEDIA_TYPE_MARKDOWN, file))
+        .build();
+
+    Response response = client.newCall(request).execute();
+    if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
+
+    System.out.println(response.body().string());
+  }
+
+  public static void main(String... args) throws Exception {
+    new PostFile().run();
+  }
+}