Issue when no GitHub token specified

[sneko]

Hi @Philmod ,

When not specifying the $GITHUB_TOKEN environment variable I receive on Slack:
Error: TypeError: Cannot read property 'author' of undefined

And in the Functions logs:
TypeError: Cannot read property 'git' of undefined at Object.module.exports.getGithubCommit (/srv/index.js:18:40) at module.exports.subscribe (/srv/index.js:48:47) at /worker/worker.js:825:24 at <anonymous> at process._tickDomainCallback (internal/process/next_tick.js:229:7)
(not the right log line since I added some logs to debug...)

I will make a PR that fixes that.

[plutov]

Same happens to me. The slack integration stopped working