Implement HTML/CSS for Admin and login pages per InVision mockups

[bglusman]

Invision mockups are linked to in README, but most of the pages don't have any kind of semi-styled version prepared anywhere. Once done in static HTML/CSS they can be easily wired into the app as Elixir/EEX templates for any dynamic content.

[dro-1]

Hello there. I'm new to open source and wondering if I cam contribute to this project?