README: Add desktop notifications instructions; Fix Heroku dyno command

[edsfocci]

I found this fix here:
https://github.com/tinyspeck/hubot-slack#hubot_slack_link_names

Sorry @robcole for not doing pull requests initially; I thought commits automatically pushed to the server, but found that they do not. Basically, I wanted to make scheduler alert users, and this was my solution.

[robcole]

Hey @edsfocci - I'm a bit confused by what you're trying to do here. All I see is a readme change - is there something else that was intended to be bundled with this PR?

Our current heroku config is set to HUBOT_SLACK_LINK_NAMES: 1, FWIW.

[edsfocci]

@robcole This is more of a reminder for those wanting to clone our project and forgets to set HUBOT_SLACK_LINK_NAMES. Also, in my experience, and Marc noticed it as well, your hubot wasn't turning @mentions into links, therefore not notifying anyone via desktop notifications. The reason why your config is set is because I told Bryan to set it before you came back, which is a major cause of confusion here.

I suppose you don't have to accept my pull request, and future users of your hubot will find out the hard way that I am correct, and they will not be desktop-notified of scheduler roundup's. I know it is just a lowly README edit, but I am finding the more experience I have in coding, the more I realize that many programmers don't place much value in documentation. Sorry to kind of take it out on you, but I am saddened by the fact that I need to spend hours in Google, Stackexchange, and Stackoverflow finding a decent working solution for something that either should've been a simple feature, or documented in the official docs.