Add invitations, guests, events, and rsvps

- Basic data model stuff for sending out invitations
- A real basic, unprotected admin page
Add basic auth to admin pages
Rename /test -> /spec
Add relationship_type to guests & names to invitations

- Add uniqueness validations for guest emails and invitation names
Add GuestImport rake task

- Make most of the objects necessary for a fun wedding by simply loading up a perfectly formed CSV
- Use Rspec instead of MiniTest
Allow nil email addresses on guest O_O

Order guests by invitation group on admin page
Add external ids to invitation
Add binding of caller gem for better errors repl
Add invitation / RSVP page

- Add factories for all the things
- Test that guest importer is idempotent
Only allow yes RSVP if an event is selected
Add Your RSVP to nav when external id is in session
Show friendly thanks flash messages on RSVP
Make events in guest importer first

- Shorter descriptions of events on RSVP page
Tweak admin page & show links to invitation forms
Admin can send invitation emails

- Use mail chimp email template
- Update mail settings