Apply website redesign rfc styles

[jenweber]

The goal of this PR is to minimally apply the website redesign styles found in ember-styleguide (ember-learn/ember-styleguide#145)

It aims to remove more CSS than it adds, and serve as a blank canvas to apply more advanced styles to after initial launch.

Changed

• colors to match the styleguide
• use grid system for sidebar layout

Removed

• a lot of CSS that could be replaced by utility classes

Needs work to reach MVP

• default link color is not accessible for regular sized text
• The search dropdowns need a lot of work, probably.
• Does nav work in fastboot?
• Needs clearer visual divisions between API methods
• Why is the navbar squished?

Screenshots

[Gaurav0]

@sivakumar-kailasam @jenweber I'd really like to see this land rather than keep it open for a very long period of time. Is there anything I can do to help?

[sivakumar-kailasam]

We have some design mocks for this app. I'll add them here later today & list items that need to be addressed that contributors can work on.

Due to the nature of the work involved, this branch will be long lived until we're ready to launch. We'll have to start creating PRs against this branch similar to what we did on the ember-wesbite repo until then.