Adds API parallelization

This change introduces a multiprocess API inspired from the way
Openstack Glance goes about spinning up its API. It creates a
parent process that forks multile child processes, each of which
host a separate eventlet wsgi server. The number of child processes
to create maybe controlled by configuration. By default, the number
of child processes brought up are equal to the number of CPUs
available on the host.
Merge pull request #340 from hmakkapati/api_parallelization

Adds API parallelization