Use six.moves cStringIO instead of cStringIO

to keep Python 3.x compatibility, use six.moves.cStringIO to
replace StringIO

Change-Id: Id89c6156d9bba0007e8b16cd2cc28413a7cc5fd3
Closes-Bug: #1280964
Merge "Use six.moves cStringIO instead of cStringIO"
(Test commit) Change README to reflect Jio's fork of Cinder

Change-Id: I3f26c0a736e63725aec24ca2fa12c707b8e6460f