Merge pull request #4 from codalab/pliang

allow everyone to access public group but not modify; fix tests
Merge pull request #11 from codalab/pliang

docker support in new worker system
Merge pull request #14 from codalab/pliang

allow uploading multiple files, JSON support
Merge pull request #18 from codalab/pliang

add instructions for cl worker with docker; fix minor bugs
Merge pull request #19 from codalab/pliang

ensure jobs are run in docker with a real username
allow user to specify default address/worksheet for new session