Add daemons to Gemfile, Daemonize update script

Summary:
	Daemonize the update script. The script now pulls, gets a list of the changed files and takes appropriate action depending on which files changed.
	Add 'daemons' to the Gemfile, which is required to daemonize the update script.

Test Plan:
	Run the update script on the server. Make a change to the repo and see if the change is pulled.
	Make a change to the update script to see if it properly restarts itself

Reviewers: bradysullivan

Differential Revision: http://hackphab.tk/D7