Update copyright and legal links
Remove link to 'Why CALs?' page
Re-word main page
Redirect to agreements index after sign-in
Replace thin with puma
Update specs to match StrongLoop workflow
Treat collaborators as though they have signed

For a workflow where an organization has dozens of repositories and
has many internal and external contributors, it is useful to not
require every existing collaborator to go through the signing process
for every repo they already have commit access to.