Facebook schedule sharing

[darrendlin]

I think share to Facebook will really be a hit, as many of our users take screenshots of their schedules and upload them to Facebook. I'm not sure if we should share the schedule URL or an image to Facebook, though. Either way the preview must show the schedule itself. Users will not need to log in to Facebook to share (see: https://developers.facebook.com/docs/sharing/reference/share-dialog)

See #12

[Bad-Science]

In light of recent events, I'm considering dropping this feature for ethical reasons. At this point, I would not like to explicitly support or reference the usage of Facebook.

In place of this, and in the interest of user choice, we could have an enhanced URL sharing feature. The linked URL would have Open Graph meta tags (http://ogp.me/), so should a user choose to share their link to Facebook, the link preview would include a snapshot of the schedule in the preview.

I believe this would require implementing Angular Universal (as per issue #36), or adding image generation on the backend.

Alternatively, we could add a backend service that generates schedule images and stores them in a CDN, and returns links to those images for sharing.

@copperwater @perribus I wonder if you have any thoughts on this :)