lucifer: Clean up

Final clean up now that design is stable.

Mostly documentation changes with some refactoring.

BUG=chromium:748234
TEST=bin/test_lucifer

Change-Id: I55c3ad1792e5aeeb98f0d205474b166021049c43
Reviewed-on: https://chromium-review.googlesource.com/714645
Commit-Ready: Allen Li <ayatane@chromium.org>
Tested-by: Allen Li <ayatane@chromium.org>
Reviewed-by: Prathmesh Prabhu <pprabhu@chromium.org>
diff --git a/venv/lucifer/conftest.py b/venv/lucifer/conftest.py
index bc5176d..bb8e7ff 100644
--- a/venv/lucifer/conftest.py
+++ b/venv/lucifer/conftest.py
@@ -19,7 +19,7 @@
 
 def pytest_collection_modifyitems(config, items):
     """Modify tests to remove slow tests if --skipslow was passed."""
-    if config.getoption("--skipslow"):
+    if config.getoption("--skipslow"):  # pragma: no cover
         skip_slow = pytest.mark.skip(reason="--skipslow option was passed")
         for item in items:
             if "slow" in item.keywords: