Add activities for events and display on dashboard

[isawpalmetto]

Devs will need to add the activity types enum and activities table to their local db. Please see db/schema.sql

Didn't want to add tests until I get some eyes on this to see if this is headed in the right direction

[isawpalmetto]

[paulsmith]

I got this error at the end of creating a new application:

2017/09/13 11:30:13 app creation failed: error adding activity: inserting into activities: pq: insert or update on table "activities" violates foreign key constraint "activities_deployment_id_fkey"