alert_syslog

Added new alerter syslog
alert_syslog to write anomalous metrics to the syslog at LOG_LOCAL4, so
LOG_WARN priority this creates in local syslog and ships to any remote syslog
as well, so that it can be used further down a data pipeline in elasticsearch,
riemann, etc
Modified:
readme.md
src/settings.py.example
src/analyzer/alerters.py