Implement secure browsing settings

[daveschaefer]

Dan Callahan has a good presentation on basic webserver security settings here: http://pyvideo.org/video/2315/quick-wins-for-better-website-security

We should enable the applicable ones for notary servers. This means:

Render: 1. Enable XSS Protection 2. Set the Content Security Policy 3. Set XFrame options

Adding SSL is covered in #19. Once SSL is enabled we can also add Strict Transport Security.

[netsafe]

done it im my NGinx config