Slack Message Builder
Slack now have a tool that does this https://api.slack.com/docs/messages/builder
See what the payload you send to a Slack chat.postMessage will be displayed like.
Slack Formatting documentation: https://api.slack.com/docs/formatting
Give it a go: http://davestevens.github.io/slack-message-builder
Development
Written in ES6 (using Browserify) and Sass.
Building
npm install
Install all required dependencies.
npm run build
Builds JS and CSS from app directory into dist directory.
npm start
Runs a local server.