Add github dispatcher to have one elegant url for both github integrations.

Dispatcher avoids to create new URL for github_webhook.

zerver/views/webhooks/github_dispatcher.py

@@ -0,0 +1,12 @@
+from __future__ import absolute_import
+from django.http import HttpRequest, HttpResponse
+from .github_webhook import api_github_webhook
+from .github import api_github_landing
+
+
+def api_github_webhook_dispatch(request):
+    # type: (HttpRequest) -> HttpResponse
+    if request.META.get('HTTP_X_GITHUB_EVENT'):
+        return api_github_webhook(request)
+    else:
+        return api_github_landing(request)