Updates the README
Updates the README

Adds some examples and removes the beta info

peernohell/node-slack-client,slackapi/node-slack-sdk,slackapi/node-slack-sdk,slackapi/node-slack-sdk,slackhq/node-slack-sdk,slackapi/node-slack-sdk,peernohell/node-slack-client,slackhq/node-slack-client