Scheduler polling is switched on dynamically based on the version of Erlang. In some cases (bugs and hangups?) the user may want to disable scheduler statistics while using newer versions of vmstats.
Make it optional, but defaulting to active to keep a backwards-compatible behaviour.
Making scheduler polling optional.
Closes issue #3
The scheduler polling will be disabled by default to avoid a few
potential bugs with the scheduler. To enable it, forcing the
env variable 'sched_time' to 'true' will required.