Adding config argument to integration test suite

This change adds a pytest config argument, allowing the integration test
suite to be run with the client configured with a specific section from
the PyKMIP configuration file. A simple integration test class is added
to demonstrate how to use the client created using the config argument.

To run the integration test suite with a specific configuration, use:

$ tox -e integration -- --config <config-section>

where <config-section> is the name of the config file section to use for
the PyKMIP client.

kmip/tests/integration/conftest.py

@@ -0,0 +1,40 @@
+# Copyright (c) 2015 The Johns Hopkins University/Applied Physics Laboratory
+# All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import pytest
+
+from kmip.services.kmip_client import KMIPProxy
+
+
+def pytest_addoption(parser):
+    parser.addoption(
+        "--config",
+        action="store",
+        default="client",
+        help="Config file section name for client configuration settings")
+
+
+@pytest.fixture(scope="class")
+def client(request):
+    config = request.config.getoption("--config")
+
+    client = KMIPProxy(config=config)
+    client.open()
+
+    def finalize():
+        client.close()
+
+    request.addfinalizer(finalize)
+    request.cls.client = client