added help button
Integrated server object to do shutdown, restart server when config changes.
Refactored server interaction into Server object; browser now launches
once server is ready
Only launch browser once.
Merged in augmentations to the  server object.

Conflicts:
	psiturk/dashboard_server.py
Merge remote-tracking branch 'nyuccl/dev' into dev
Merged in dev changes.
Fixed data write error in the example experiment.
Trial data can now be downloaded.