Merge pull request #359 from Automattic/ui-tweaks

Minor CSS tweaks & tagline change
Merge pull request #360 from Automattic/ui-tweaks

Ability to filter modules by category
Random redirect: No need to check for conflicts on wpcom.
Custom CSS: Remove code that should not be in Jetpack

Merges r93900-wpcom.
Correct version of 6df037d

The function `_x` only takes three parameters.
SSO: Fix issues with WP logo on button.

Previously it didn’t account for core’s button resizing breakpoint.  By
changing it to a flexible height, it will fit anything going forward.
Updated module descriptions & icons added to JP homepage

- Updated module descriptions
- icons on homepage
- Removed dummy “config” link from homepage “learn more” modal