Add base test class for unit tests

This commit adds a base test class for the tempest unit tests. The
base class uses fixtures to capture STDOUT and STDERR as well as
providing an interface to use mox to stubout tests.

Change-Id: Ia60cccd77cfb6489f888ff088351fe267115a22f
diff --git a/test-requirements.txt b/test-requirements.txt
index 8aa6ed9..fbe7e43 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -4,3 +4,4 @@
 sphinx>=1.1.2
 python-subunit
 oslo.sphinx
+mox>=0.5.3