Add PHPFPM stat

- HTTP status or Socket status
- Collect those metric:
    accepted conn:
    listen queue:
    max listen queue:
    listen queue len:
    idle processes:
    active processes:
    total processes:
    max active processes:
    max children reached:
    slow requests:
- Tag metric with: `host` and `pool` name

Closes #255

plugins/all/all.go

@@ -14,6 +14,7 @@ import (
 	_ "github.com/influxdb/telegraf/plugins/mongodb"
 	_ "github.com/influxdb/telegraf/plugins/mysql"
 	_ "github.com/influxdb/telegraf/plugins/nginx"
+	_ "github.com/influxdb/telegraf/plugins/phpfpm"
 	_ "github.com/influxdb/telegraf/plugins/ping"
 	_ "github.com/influxdb/telegraf/plugins/postgresql"
 	_ "github.com/influxdb/telegraf/plugins/procstat"