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.
Update spec to remove deprecation warnings
Allow agreement creation to be restricted

By setting the ADMIN_REPO environment variable, only users who are
collaborators on that repo are allowed to create new agreements.
Add option for restricting repo selection

By setting the ALLOWED_ORGS environment variable to a comma separate
list of orgs, only repos owned by those orgs can have agreements
created for them.
Auto-paginate GitHub queries

The per_page option is capped at 100, and nothing was actually handling pagination anyway.
Add support for supplemental seed data
Enable upsert behaviour of create_hook
Allow hooks to be updated if they already exist
Replace thin with puma
Initial rebranding
Update copyright and legal links
Remove link to 'Why CALs?' page
Re-word main page
Redirect to agreements index after sign-in
Update specs to match StrongLoop workflow
Replace icons with StrongLoop icons
Replace icon logo with proper sized image
Remove CLAHub reference from title
Update home page layout/wording