Auto-unsubscribe from the hackmap issue after posting

[waf]

From discussion on #10 by @ches:

everyone who adds a hack gets subscribed to the issue and gets email notifications for subsequent posts—kind of cool network effect of hearing about what others are doing, but also potentially annoyingly noisy to some

Initial thought is for the app to call DELETE /notifications/threads/:id/subscription (or some other API?) to prevent email notifications.

[djay]

@ches @waf I think notifications are a feature rather than a problem as long as they are only on new comments/hacks rather than every update or move.
We could have a button on the page for users to optionally unsubscribe though.

[waf]

closing this, as it's not clear if it's a bug or a desired feature 😄

each notification sent from github comes with a direct link to unsubscribe, so I think that's fine.