fix meminfo output on consecutive calls

There are two possible error scenarios for CallPgrep.  

try to fix diskio stats on FreeBSD-10.x

FreeBSD apparently changed the magic sysctl mib values for devstats.

    --- FAIL: TestDisk_io_counters (0.00s)
    disk_test.go:39: error no such file or directory
    disk_test.go:42: ret is empty, map[]

This code uses an undocumented, but exported, go stdlib method to fetch
the sysctl by string instead of mib.

system (no pgrep command) and one is a normal error state of pgrep
meaning no processes found for the criteria given (in this case the parent
pid does not exist or the process simply has no children).  The later case
is quite usefull to know about so I added a static error for this case.

host_linux: Skip everything that isn't a normal process.

Matches the host_linux change.

host_darwin does the same filtering. Not doing this gives us some rather strange
entries that likely aren't what we want.

Before:
    {"user":"reboot","terminal":"~","host":"3.10.0-327.4.5.el7.x86_64","started":1454378260}
    {"user":"LOGIN","terminal":"ttyS0","host":"","started":1454378270}
    {"user":"LOGIN","terminal":"tty1","host":"","started":1454378270}
    {"user":"runlevel","terminal":"~","host":"3.10.0-327.4.5.el7.x86_64","started":1454378276}
    {"user":"root","terminal":"pts/0","host":"vpn","started":1454404513}

After:
    {"user":"root","terminal":"pts/0","host":"vpn","started":1454404513}

fix callps command generate error

[WIP] net,process[linux]: add process.NetIOCounter and net.NetIOCounterByFile.

Add -a when calling ps on darwin

Optimize per-process percentage calculation

Get Arch Linux Version from LSB

format go program with go 1.5.2 "go fmt"

fix typos

Add nf_conntrack counter support

Add -W flag to netstat on BSD systems

CPU race condition fix

This prevents netstat from truncating the interface name to 5
characters. See https://github.com/influxdb/telegraf/issues/438

process[darwin] Fix unit of RSS and VMS

using HostProc for protocounters in linux

Should be bytes, `ps` returns Kbytes.

[net] fix panic on freebsd (netstat error with exit code 0)

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