Horizon test setting no longer depends on nose and related stuffs.
This commit cleans up nose related dependencies.
Filenames of test modules need to start with test_*
so that Django test runner detects them.
There is no test defined but it would be nice to adjust the filename.
Also moves horizon dependencies to requirements.txt.
Change-Id: Ib2f246d76da8a1f5d26a9cf8e9ef27e5f4f62bee
baeb8879a2