Plans: A/B test displaying a feature list vs. description in Plan

[drewblaisdell]

Fixes #2752.

Testing
With a description

• Visit http://calypso.localhost:3000/start in a new browsing session.
• Run localStorage.setItem( 'ABTests', '{"plansFeatureList_20040201":"description"}' ); in your browser.
• Proceed through signup to the plans step.
• Assert that you see a sentence as the description for each plan.
• Assert that you see the same description on /plans/:site after signing up.

With a list of features

• Visit http://calypso.localhost:3000/start in a new browsing session.
• Run localStorage.setItem( 'ABTests', '{"plansFeatureList_20040201":"list"}' ); in your browser.
• Proceed through signup to the plans step.
• Assert that you see a list of features (like in the screenshot above) for each plan.
• Assert that you see the same list of features on /plans/:site after signing up.
• Product review
• Code review

cc @danhauk

[breezyskies]

Looks good! A couple nitpicks:

1. On the /plans page for logged in users, the "never expires" and space below looks off. I'd just hide this entirely so it looks like the signup version:

2. I'd bump the top / bottom padding on the features up to 5px.

[drewblaisdell]

@breezyskies Thanks for the feedback. I updated the commit with those changes.

[breezyskies]

Looks good. 👍

[scruffian]

Code 👍

[drewblaisdell]

cc @lucasartoni to make sure that it's cool to run this concurrently with the periodLabelFree test.

Edit: He confirmed on Slack, so we're good-to-go here.