Use a helper to add Glyphicons
Let the view decide which nav links to show
Add titles to nav links
Extract "back" group view path logic into helper
Replace nav link labels with icons
Merge pull request #3 from CoCycle/user-interface

Navigation between group views now uses icons instead of labels.

- Views have been cleaned up with a Glyphicon and "back" path helper
- The decision of whether to show a nav link for a particular view has been moved into to the nav partial