Makes use of requests.Session
Makes use of requests.Session

This allows better connection pooling and may improve performances.

Change-Id: I69e986b7387dd3ac281731b8355a3eec34a537f8

zackmdavis/python-swiftclient,pratikmallya/python-swiftclient,jeseem/python-swiftclient,sohonetlabs/python-swiftclient,VyacheslavHashov/python-swiftclient,VyacheslavHashov/python-swiftclient,jeseem/python-swiftclient,ironsmile/python-swiftclient,openstack/python-swiftclient,JioCloud/python-swiftclient,sohonetlabs/python-swiftclient,varunarya10/python-swiftclient,iostackproject/IO-Bandwidth-Differentiation-Client,iostackproject/IO-Bandwidth-Differentiation-Client,openstack/python-swiftclient,ironsmile/python-swiftclient,pratikmallya/python-swiftclient,zackmdavis/python-swiftclient,krnflake/python-hubicclient,JioCloud/python-swiftclient,varunarya10/python-swiftclient