Added license

LICENSE.md

+Copyright 2012-2013 Elasticsearch BV
+
+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.