Added predis to use redis.
Implemented webhook endpoint.
Implemented webhook preview page.
Updated README to add webhook description.
Updated README to add redis setup.
Added menu page.
Updated README to add menu description.
Implemented webhook prepare.
Fixed to apply webhook prepare logic.
Updated README to add webhook prepare description.
Fixed to spell out.
Added css style.
Changed console.debug for IE.
Remove preview to improve webhook demo.
Small UI Improvement
Renamed webhook_prepare to webhook.
Updated README to add demo description.
Patched with following diff
 - https://gist.github.com/matsubo/4a71d8d5a4adf7571b09
Added getallheaders function.
Added document and correct sentence