Added button. Needs more styling.
Merge branch 'staging' of https://github.com/code-dot-org/code-dot-org into hoc_all_events_button
Added button above HOC map that links to /events page.
Added a bottom-margin so that the button would look better on small screens
Merge pull request #394 from code-dot-org/hoc_all_events_button

Hoc all events button