Wrap Django runserver to prevent spammy logging.

Django's `manage.py runserver` prints a relatively low-information log
line for every request of the form:

[14/Dec/2015 00:43:06]"GET /static/js/message_list.js HTTP/1.0" 200 21969

This is pretty spammy, especially given that we already have our own
middleware printing a more detailed version of the same log lines:

2015-12-14 00:43:06,935 INFO     127.0.0.1       GET     200   0ms /static/js/message_list.js (unauth via ?)

Since runserver doesn't have support controlling whether these log
lines are printed, we wrap it with a small bit of code that silences
the log lines for 200/304 requests (aka the uninteresting ones).

tools/run-dev.py

@@ -77,7 +77,7 @@ os.setpgrp()
 # zulip/urls.py.
 cmds = [['./tools/compile-handlebars-templates', 'forever'],
         ['./tools/webpack', 'watch'],
-        ['python', 'manage.py', 'runserver', '--nostatic'] +
+        ['python', 'manage.py', 'rundjango'] +
           manage_args + ['localhost:%d' % (django_port,)],
         ['python', 'manage.py', 'runtornado'] +
           manage_args + ['localhost:%d' % (tornado_port,)],

zerver/management/commands/rundjango.py

@@ -0,0 +1,13 @@
+# Wrapper around Django's runserver to allow filtering logs.
+
+from django.core.servers.basehttp import WSGIRequestHandler
+orig_log_message = WSGIRequestHandler.log_message
+def log_message_monkey(self, format, *args):
+    # Filter output for 200 or 304 responses.
+    if args[1] == '200' or args[1] == '304':
+        return
+    return orig_log_message(self, format, *args)
+
+WSGIRequestHandler.log_message = log_message_monkey
+
+from django.core.management.commands.runserver import Command