bug fix- typo in variable name from daemonize
added scheduler sync to backend

added a smart sync for the scheduler to the backend so that we
can get the latest frequency changes without overwriting our
last run time
added scheduler to centinel runtime

added a scheduler to the centinel runtime so that we can set
experiments to run with some frequency and we will preempt if we
are running the experiment too frequently. we are still dependent
on something like cron to run centinel itself, but this lets us
change the run frequency for individual experiments
Merge pull request #100 from ben-jones/add_scheduler

Add scheduler