Remove invalid HTTP header "Link"

Not only is it not a valid HTTP header but it also doesn't exist in the API.
started on a registration form
including validators from original pypi
Added created_account page + form to register

* modified engine to query app directly, allowing transacted methods
Fixing and adding tests

* fixing tests with using a connections vs an engine directly
* adding tests for user registration
adding more tests
adding itsdangerous, starting on confirmation workflow
started work on activation db method
rewriting is_email_active with the proper logic
Finishing touches for v1 of registration flow

* fixing tests
* getting coverage to 100%
* fixing flake8 issues
adding 'secret_key' field to developer config
fixing some issues r1chardj0n3s pointed out