Support work with etcd as a cluster

In case if one member of a cluster is not available it will retry with
another one and fetch the new cluster configuration. Default timeout for
all requests to etcd is 5 seconds.
Initial cluster configuration can be resolved through:
1) /v2/members call on one of the cluster members on a client port
2) when it is possible to resolve hostname into multiple ip's  it will
iterate through list and try to perform action from 1)
3) If there is discovery_srv defined in etcd section of config file it
will resolve peer addresses of all cluster members and will fetch
cluster configuration with using peer protocol by doing /members call on
a peer port

setup.py

@@ -102,7 +102,8 @@ def setup_package():
     # Some helper variables
     version = os.getenv('GO_PIPELINE_LABEL', VERSION)
 
-    install_reqs = get_install_requirements('requirements.txt')
+    requirements = 'requirements-py2.txt' if sys.version_info[0] == 2 else 'requirements-py3.txt'
+    install_reqs = get_install_requirements(requirements)
 
     command_options = {'test': {'test_suite': ('setup.py', 'tests')}}
     if JUNIT_XML: