whitespace tidy
Fix bin/rails

Frankly not sure what had happened here, but the bin/rails
we had picked up from somewhere didn’t work – couldn’t run
rails commands form the engine directory. Fixed by bringing
a fresh bin/rails over from a new, clean engine.
Add FactoryGirl to rspec.
Invitations can be found by the names of the guests attached to them.
Add .ruby-version
Remove accidental focus
Run specs tagged with :focus by default

Run all if no tag present.
Basic controller, specs and routes for retrieving an invitation
Add .ruby-gemset to gitignore