This enable vieiwing applications logs directly in grafana, as long as
loki agent can access the log file and the regular expressions to parse
the logs are defined

Other changes:
 - provision data sources automatically so that user do not have to add
   them manually
 - update TODO in README
 - introduce a SR test
 - switch to dep to install dependencies, because that's how these
  packages manage their dependencies.

Versions up:
  grafana: v6.3.0
  telegraf: v1.11.1-0
  influxdb: v1.7.8rc1
New:
  loki: v0.3.0