1. the disk io statistic data as: nread, nwritten, reads, writes, rtime, wtime;
2. the free memory under global zone;
3. the net io statistic data as: rbytes64, ipackets64, idrops64, ierrors, obytes64, opackets64, odrops64, oerrors.
The new feature branch adds the above missing statistic data based on the psutil project (https://psutil.readthedocs.io/), it has been tested under solaris ( Oracle Solaris 11.4 X86) and illumos (OmniOS v11 r151044).
This enables using gopsutil in a codebase that gets built on other OSes
than the ones supported. Instead of a build failure as before, due to
the build tags, gopsutil will now throw an "not implemented" runtime
error.
Fixes#234.
Steve Zhang