Setup the ability for people to login and create 'saved lists' of issues

To be shared at workshops or meetups. Doing this would help meetup organizers (and code-school teachers?) run open source nights where items that are currently needed can be hit. It would also allow core team members to bring attention to major items they'd like help with.
- [ ] work out UI / messaging around this to make it unobtrusive but easy to find for folks looking for it
- [ ] setup Github authentication (https://github.com/ember-learn/ember-help-wanted/issues/65)
- [ ] work through data structures for this (current thought is to have a `/lists` or `/events` endpoint with a list editable only by the user who created it). We may also want to have additional fields that a list creator can fill in (brief notes to display above the list that would allow linking out to a UseCanvas file for instance). Make it markdown and fairly short? We may also want to allow a list organizer to make brief notes on each of the issues, allowing them to provide additional detail / thoughts about items and the value of working on them)
- [ ] setup authorization rules to enforce the above so that only the user who created the list can edit it
- [ ] setup `/lists//` routing on the Ember side of things to display the appropriate data
- [ ] tests for all of the above