Completes #17
-Adds route and action for sending current_user a demo card
-Adds flash area to application layout for success message (this is expected by other actions as well)
-Test
bugfix in which all spacecraft were called ISS during pass advance notify
Merge pull request #18 from nelsonblaha/master

fix subscription associations
Merge pull request #19 from nelsonblaha/demo_card

Multi-purpose pull request
add attribute accessor for spacecraft endpoint