Onboading process [In Progress]

What this PR includes:
* Document class for storing PDFs
* `wicked_pdf` implementation for generation of PDFs (Authorizations to Release Medical Records)
* UI for on-boarding patients (personal info, provider selection, authorization)
* Mailer to notify admins of new authorizations (with documents attached)
* Fix for subheader `<a>` tag line-height (https://github.com/PatientBank/Core/issues/74)
* Documents view (`/documents`)