first pass at adding stats for OS-X to the Stats class -- incomplete
final update -- all deltas from le:

. tidied/corrected system information sent to le for OS-X

. added code to check for alternate stats gathering routines if proc
  filesystem isn't present -- alternate path based on system type reported
  by uname

. added osx_top_stats function, within class Stats, to pull CPU usage,
  memory usage, and very crude disk IO from the header of top(8).  See
  internal commentary for further rationale.

. added netstats_stats function, within class Stats, to pull network
  bandwidth information from netstat(8)

I'm a perl programmer -- this is my first serious attempt at python.  Lots
of looking at how things are done elsewhere in the code, getting answers
from the online python manual, pydoc, and of course, google/Stack Overflow.
I wouldn't really throw this at a production system without a review by a
python coder.

The one thing that bugs me, and google hasn't helped much with, is finding
a nice self-contained way to 'close' the output pipes I open with:

    proc = subprocess.Popen(['top', ...],stdout=subprocess.PIPE)

...surely that's necessary?
Merge pull request #14 from trjh/master

Additional data/stats for OS-X