Using host Linux (Ubuntu 12.04); performance was abysmal.

On initial load of localhost:4000, the http calls for
additional Javascript files via the browser appears to take
more than a few minutes with *.js endpoints loading in one
file at a time very slowly.

It was observed that the Ruby process was consistently
pegged at 95% and up.  This behaviour is not observed
using a Mac OSX.

However, adding a single core to the guest OS
(from 1 to 2) improved performance considerably.

The patch detects if the host system is Mac OSX or
Linux and attempts to assign the same number of cores
as is present on the host.