feat: add license in README

README.md

@@ -51,3 +51,21 @@ None
   * install bundler `gem install bundler`
   * install dependencies `bundle install`
   * run the tests `rake`
+
+## License
+
+```
+Copyright (c) 2017 Adrien Waksberg
+
+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.
+```