pleaase fix problem with gopsutil bug

[yosefy]

it shows wrong metrics now.
shirou/gopsutil@28640e5

also there is typo in code:
in
https://github.com/influxdata/telegraf/blob/master/plugins/inputs/procstat/spec_processor.go:

if err == nil {
    fields[prefix+"read_count"] = io.ReadCount
    fields[prefix+"write_count"] = **io.WriteCount**
    fields[prefix+"read_bytes"] = io.ReadBytes
    fields[prefix+"write_bytes"] = **io.WriteCount**

problem looks like that:
procstat,host=pa-live-publish21,pidfile=/var/run/WowzaStreamingEngineManager.pid,process_name=java cpu_time_guest=0,cpu_time_guest_nice=0,cpu_time_idle=0,cpu_time_iowait=0,cpu_time_irq=0,cpu_time_nice=0,cpu_time_soft_irq=0,cpu_time_steal=0,cpu_time_stolen=0,cpu_time_system=3148.26,cpu_time_user=6144.58,involuntary_context_switches=3i,memory_rss=94728192i,memory_swap=0i,memory_vms=5102858240i,num_fds=57i,num_threads=30i,pid=25450i,read_bytes=0i,read_count=14372i,voluntary_context_switches=6i,write_bytes=105i,write_count=105i 1470250276000000000

shirou/gopsutil@28640e5

thanks

[yosefy]

also it wont output io metrics for process when running as telegraf (not root ) user
thanks

[sparrc]

dupe of #1584