Use shinier menu icons

Summary:

• Use @chad's nice gradient overlay icons.
• Show selected states.
• Use profile picture for profile item (not sure about this treatment?)
• Workflow the logout link

Test Plan: Will add screenshots.

Reviewers: alanh, btrahan, chad

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D3225