Fixed link.
Added Introduction and Round Info
Update page-challenge-details.php

Added documents list for Design challenges
Added Downloads list for development challenges
Added Platforms list
Added basic info for marathon challenges
Added NA until API is updated.
Revert "Build PHP based SSO Callback"

This reverts commit 545a6110ecfa92951b1d3d2a2a8f20567109f9a5.
Merge branch 'master' into TC-Community-2014-02-12