Modify landing page design.

The changes here are tentative and ideally will bring up some discussion
(@jhladky, thoughts?).


## Changes:
   * Underline sections on the landing page
   * Move sticky posts above the 'Club News' section
   * Add a radial gradient for the background

## Needed changes (not tentative)
   * Update Projects Manager to Alfredo Sanchez for 2014-2015 year
   * Move tutoring under the outreach tab