Common internal

cpu: support ARM CPUs.

Package common wasn't used for public functions. Place it in an
internal directory to prevent other packages from using.

Remove the distributed references to "HOST_PROC" and "HOST_SYS"
consts and combine into a common function. This also helps so that
if a env var is defined with a trailing slash all will continue to
work as expected.

Fixes #100

chore(*): Fixes #94

ARM CPUs don't include the same fields as  x86 and amd64 CPUs in
the /proc/cpuinfo list. Pull information from the /sys/...
device tree as well as updating when a CPU is done in cpuinfo.

Fixes #88

Added the ability to fetch an alternative location for /proc via an
environment variable. If the env var is not set it will return /proc as
the default value.

shirou/gopsutil#90 make hostinfo more robust

cpu[darwin]: separetes cpu_darwin into cgo and nocgo to get CPUTimes.

CreateTime() on linux returning an incorrect timestamp

Fix docker on Centos 7

When MemAvailable is in /proc/meminfo, use it (kernel 3.14+)

Use vm_stat command on darwin to get memory

This has the benefit of allowing us to also grab the cached memory so
that we can get an "available" measurement

process[linux, darwin]: implements Connections using lsof.

Support 32-bit linux, this field is int32 on 32-bit systems

Add process/Parent, net/NetConnections on darwin and linux