Daemonize and tail event log

Rough draft needs work. The idea here is to have a
standalone daemon monitor an event log, detect a DOS
attack and then write a DOS status event to a different log.
This log will be monitored by OSEC... which will perform
a mitigation action.
Merge branch 'feature/dos-mitigation' of github.com:ehartsuyker/securedrop into feature/dos-mitigation

I manually resolve the conflicts in:
	modules/deaddrop/files/deaddrop/dos_mitigation.py
Clean up code a bit and add doc string
Merge pull request #1 from david415/feature/dos-mitigation

Daemonize and tail event log