Update README instructions on using the dashboard
Update README instructions on using the dashboard

Provide additional instructions to allow users of the image to get started quicker including the default login credentials as well as how to configure the Graphite data source.
kevintvh/docker-grafana-graphite,kevintvh/docker-grafana-graphite,dortizesquivel/docker-grafana-graphite,baardl/docker-grafana-graphite,dokku/docker-grafana-graphite,Andro999b/graphite-grafana,ImmobilienScout24/docker-grafana-graphite,pastcompute/docker-grafana-graphite,abarbanell/docker-grafana-graphite,jarek-przygodzki/docker-grafana-graphite,ImmobilienScout24/docker-grafana-graphite,kamon-io/docker-grafana-graphite,dokku/docker-grafana-graphite,baardl/docker-grafana-graphite,abarbanell/docker-grafana-graphite,pastcompute/docker-grafana-graphite,ImmobilienScout24/docker-grafana-graphite,iheartradio/docker-grafana-graphite,sekka1/docker-grafana-graphite,jarek-przygodzki/docker-grafana-graphite,Andro999b/graphite-grafana,iheartradio/docker-grafana-graphite,jhu-chang/docker-grafana-graphite,abarbanell/docker-grafana-graphite,jhu-chang/docker-grafana-graphite,santanusinha/docker-grafana-graphite,dokku/docker-grafana-graphite,baardl/docker-grafana-graphite,kevintvh/docker-grafana-graphite,jacklcz/docker-grafana-graphite,kamon-io/docker-grafana-graphite,jarek-przygodzki/docker-grafana-graphite,iheartradio/docker-grafana-graphite,rolestar/docker-grafana-graphite,rolestar/docker-grafana-graphite,jacklcz/docker-grafana-graphite,jhu-chang/docker-grafana-graphite,rolestar/docker-grafana-graphite,santanusinha/docker-grafana-graphite,kakiezhang/docker-grafana-graphite,sekka1/docker-grafana-graphite,Andro999b/graphite-grafana,jacklcz/docker-grafana-graphite,kamon-io/docker-grafana-graphite,kakiezhang/docker-grafana-graphite,santanusinha/docker-grafana-graphite,dortizesquivel/docker-grafana-graphite,pastcompute/docker-grafana-graphite,kakiezhang/docker-grafana-graphite,sekka1/docker-grafana-graphite,dortizesquivel/docker-grafana-graphite