Add Yahoo copyright

Author: ericf

src/index.js

@@ -1,3 +1,9 @@
+/*
+ * Copyright 2015, Yahoo Inc.
+ * Copyrights licensed under the New BSD License.
+ * See the accompanying LICENSE file for terms.
+ */
+
 import * as p from 'path';
 import {writeFileSync} from 'fs';
 import {sync as mkdirpSync} from 'mkdirp';