Add Prometheus Pushgateway to the docker-compose infrastructure.

Fix typo

update Alertmanager to v0.14.0
fix #59

Grafana 4.6.2 -> 4.6.3

Alerting rules update

Seems these three rule alert files were merged into `alert.rules`, changed `prometheus.yml` to update this. `README.md` references the three missing rule alert files and should be updated as well.

Turns out 4.6.3 is the latest release version https://github.com/grafana/grafana/blob/master/CHANGELOG.md

Alertmanager v0.13.0

disable cgroup mount for macOS
ref #43

added line to enable Lifecycle APIs

The --web.enable-lifecycle flag controls HTTP reloads and shutdowns in
Prometheus. Disabled by default in v2.0

Prometheus 2.0

added cgroup mount to fix Ubuntu16.04 cadvisor issue

automatically install grafana datasource and dashboards

using script taken from https://github.com/grafana/grafana-docker/issues/74

Force docker to start nodeexporter as root and in privileged container

Fix for #29

possible fix for #30

Pin Docker images to specific tags and fix node-exporter incompatibility

Prometheus pinned at: v1.8.0
Node-exporter pinned at: v0.15.0