<http://schema.org/headline>
"Webhook\u3092\u6D3B\u7528\u3057\u305F\u958B\u767A\u652F\u63F4\u306E\u5E83\u304C\u308A"^^<http://www.w3.org/2001/XMLSchema#string>
<http://gihyo.jp/dev/column/newyear/2015/spread-of-development-support-utilizing-webhook>