Replace test runners with nose, and add tox support.

Reviewed in: https://codereview.appspot.com/6490081/
diff --git a/.hgignore b/.hgignore
index 9406408..38ec00f 100644
--- a/.hgignore
+++ b/.hgignore
@@ -7,6 +7,7 @@
 */.git/*
 */.cache/*
 .gitignore
+.tox
 samples/buzz/*.dat
 samples/moderator/*.dat
 htmlcov/*