Add privacy and terms of use links to footer.

Closes #24.
Merge branch 'issues/24-footer-links'
Change topnav items

Use http://tuderechoasaber.es/ items
Merge branch 'issues/13-topnav'
Add Terms of Use sign up confirmation
fixup! f9a63a4dc3451917bf25c4f87bafe1e0902a3bc0 terms message
fixup! 97d796a01d0c5994542939748c9f94a12c9d79f6 fix spec
fixup! f9a63a4dc3451917bf25c4f87bafe1e0902a3bc0 fix checkbox with errors style