Give user an amplify button. See issue #121

Create a migration for an amp table linking event and users. Also created controller for Amps to handle create and new amps.

Once a user has amplified an event, show the event as having been amplified.

Added controller, button to view

WIP - show user that they've amplified an event

Show user that they've amplified an event
Merge pull request #134 from southpolesteve/amp

Give user an amplify button. Closes #121