This commit includes layout changes suggested by Christophe, and some CSS modifications to make the 'fork on github' ribbon scroll properly.

changed worksheet links to match updated filenames in io.

Updated links to codalab.github.io
Merge pull request #456 from willum070/landingpage

This commit includes layout changes suggested by Christophe
deleted obsolete competition example files
Remove use of deprecated option --use-mirrors.
Merge branch 'examples' of https://github.com/willum070/codalab into cleanup
Merge branch 'cleanup'
Make name of submitter and submission date available to competition scoring program.
Merge branch 'master' of https://github.com/codalab/codalab
Merge pull request #459 from cpoulain/master

Make current submission info available to scoring program
Merge branch 'master' of https://github.com/codalab/codalab into dev