Use https image.
Add a background color.

Differentiates the page from the background.
Update the landing page.

Includes instructions for getting setup.
Add border around inline code snippets.
Emphasize instructions in Getting Started guide.
Filter lessons by type.

Used by the API to retrieve a list of challenges
(without articles).
Rearrange sample article structure.

Putting them in their own folders allows us to include additional
assets (e.g. images, sample code).
Package archive for challenges.
Remove focus: true.
Prepare sample challenge.
Add more info to getting started page.
Merge pull request #57 from atsheehan/getting_started

Getting started