Pivotal Tracker API
- Added serializers for iteration
- Added serializers for activities
- Added custom buildurl for activities
- Moved loading.hbs to /scrum/ as ember (for some reason) expected to find it in that folder
- Updated handlebar tags
- Fixed a bug in iteration serializer where sideloading json was done improperly

TODO:
- Stories are still not displayed properly
- serialize ProjectMembers/StoryOwners 'Person' model