Add configuration docs to Postgresql input plugin

plugins/inputs/postgresql/README.md

@@ -29,3 +29,28 @@ _* value ignored and therefore not recorded._
 
 
 More information about the meaning of these metrics can be found in the [PostgreSQL Documentation](http://www.postgresql.org/docs/9.2/static/monitoring-stats.html#PG-STAT-DATABASE-VIEW)
+
+## Configruation
+Specify address via a url matching:
+
+  `postgres://[pqgotest[:password]]@localhost[/dbname]?sslmode=[disable|verify-ca|verify-full]`
+
+All connection parameters are optional. Without the dbname parameter, the driver will default to a database with the same name as the user. This dbname is just for instantiating a connection with the server and doesn't restrict the databases we are trying
+to grab metrics for.
+
+  `address = "host=localhost user=postgres sslmode=disable"`
+
+A  list of databases to explicitly ignore.  If not specified, metrics for all databases are gathered.  Do NOT use with the 'databases' option.
+
+  `ignored_databases = ["postgres", "template0", "template1"]`
+
+A list of databases to pull metrics about. If not specified, metrics for all databases are gathered.  Do NOT use with the 'ignore_databases' option.
+
+  `databases = ["app_production", "testing"]`
+
+### Configuration example
+```
+[[inputs.postgresql]]
+  address = "postgres://telegraf@localhost/someDB"
+  ignored_databases = ["template0", "template1"]
+```