Add PyECLib as a requirement

Swift will call into PyECLib for erasure coding functions.
This is in preparation for the change in review:
   https://review.openstack.org/#/c/66482

PyECLib is BSD licensed.

Change-Id: I0884256fa9e65101ff7673a32eea0ecea0ad257b
Signed-off-by: Tushar Gohad <tushar.gohad@intel.com>
Merge "Add PyECLib as a requirement"