contact.jade: Split location off to its own page
contact.jade: Remove usage of line breaks

* style.css: Introduce CSS selectors 'padding-top-offset10',
'padding-top-offset20' and 'label'.
layout.jade: Bit of polish on site footer

* contact.jade: Move Privacy Policy link to site footer.
* Add my copyright.

* Remove footer's site navigational links.
* Remove usage of line breaks; introduce 'margin-top-offset20'
CSS selector.
Introduce web form to email functionality with SendGrid

Mock email objects in the development environment, and the real deal
in testing and production environments.

By default, both plain-text and HTML email copies are sent,
leaving it up to the email client which to prefer displaying.

* Introduce 'testing' environment option.

* contact_success.jade: Relocate the tabular display of contact form
fields to views/email_html_template.jade; this is to support HTML
emails.

* Introduce views/email_text_template.jade; this is to support
plain-text e-mails.

* README.md: Add some documentation for what happens in testing
and production environments, and include info on how to set the
SENDGRID user name and password environment variables.
package.json: Mark our site app private && specify specific node ver