Support for upgrading the cpool nif
Move away from passing in scheduler_id

Look it up instead. Slightly less efficient,
but god damn is that edge condition common
when under load.
Fix another double-free error

Much rarer condition. Namely, occurs when the
scheduler preempts a process before calling into
a CQueue function, and then migrates the process
to another scheduler while it's idle, resulting
in an incorrect scheduler_id value and opening a
window for two schedulers to be modifying the
same list.
DEBUG: on_upgrade debug message
DEBUG: debug message for registering schedulers
RELEASE 1.1.0b

HOTFIX RELEASE
Account for a condition where two schedulers could be
modifying the same list by not relying upon the
scheduler ID that's being passed in.