Make it a little easier to run specific tests

Changes ./bin/test.sh to pass command line options to pytest, and default to
only running tests in the tests/ directory instead of everywhere excluding
a few directories which is more error-prone.

Also keeps the mock_server used in testing quiet so access log entries don't
appear on stdout.

tests/mock_server/server.py

@@ -50,4 +50,4 @@ def redirect_to_static(filename):
 
 
 def start():
-    run(host='localhost', port=8080)
+    run(host='localhost', port=8080, quiet=True)