Removed runserver command. (#1897)

Runserver is added to Daphne in django/daphne#429 allowing users of
other ASGI servers to use Channels without requiring Daphne and
Twisted.

To use add daphne to INSTALLED_APPS before django.contrib.staticfiles:

INSTALLED_APPS = [
    "daphne",
    ...
]

channels/apps.py

@@ -1,19 +1,7 @@
-# We import this here to ensure the reactor is installed very early on
-# in case other packages accidentally import twisted.internet.reactor
-# (e.g. raven does this).
-import daphne.server
 from django.apps import AppConfig
 
-assert daphne.server  # pyflakes doesn't support ignores
-
 
 class ChannelsConfig(AppConfig):
 
     name = "channels"
     verbose_name = "Channels"
-
-    def ready(self):
-        # Do django monkeypatches
-        from .hacks import monkeypatch_django
-
-        monkeypatch_django()