Campaign tracking

[forrest]

Attach a campaign event to a visitor any time they come from one of our various sources. This can probably be added in the middleware to detect the UTM parameter already used by google analytics.

• An interface that let's you see the overal traffic form your campaigns, as well as the number of visitors, signups, upgrades, etc.
• Probably let the user set which events should be followed with a campaign.
• Some fields to include $ spent or number of people it was sent to. This could be helpful for measuring the long term ROI.