Fingerprint users

[jace]

Based on hasgeek/baseframe#124, Hasjob should record browser fingerprints against the event session as an additional column, or in a separate table that stores component data.

Since fingerprints are sensitive to the browser version, they have no historical value identifying users across sessions (cookies do that and our cookies are permanent anyway). Fingerprints are more useful tracking the user across our websites within a limited period -- if, for example, an anonymous user followed a Hasjob campaign for an event and subsequently bought a ticket. We can currently use GA to confirm the buyer came from Hasjob, but we can't link it back to any browsing activity within Hasjob. Having the same fingerprint on both sides will help understand user flow better.