Remove httpretty from explicit requirements (a working version is now being set by moto https://github.com/spulec/moto/commit/2e69986e01caa6d2f8acbcb286a5c0a9c09c6ce2)

setup.py

@@ -22,8 +22,7 @@ openstack_reqs = ['python-novaclient>=2.33.0',
                   'python-keystoneclient>=2.0.0']
 aws_reqs = ['boto>=2.38.0']
 full_reqs = base_reqs + aws_reqs + openstack_reqs
-dev_reqs = (['httpretty>=0.8.10', 'tox>=2.1.1', 'moto>=0.4.20',
-             'sphinx>=1.3.1'] + full_reqs)
+dev_reqs = (['tox>=2.1.1', 'moto>=0.4.20', 'sphinx>=1.3.1'] + full_reqs)
 
 setup(name='cloudbridge',
       version=version,