Update README.md

Add license to readme.md

Author: Hüseyin Serkan Özaydin

README.md

@@ -85,3 +85,19 @@ public void onFail(String err) {
 });
 
 ```
+# License
+<pre>
+Copyright 2018 Huseyin Serkan Ozaydin
+
+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.
+</pre>