add landing page or a way to see how it works

[prestonp]

This came up at the last meeting, I think some folks load the app but don't really get what it is. I had a couple of ideas to fix the experience for first time users:

• Add a question mark icon somewhere that opens a helpful modal with explanations
• Add a guided tour like http://github.hubspot.com/shepherd/docs/welcome/. It would be nice if it only showed up for first time visitors.
• Make a landing page (not a fan of this tho)

[luqmaan]

A landing page can be good for SEO, because it lets us put text that is there before the app renders.

Also, the shepherd thing is great idea.