Nightly: Add script for testing nightly builds

.circleci/trigger-nightly-build.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+# Triggers a nightly build for the latest commit on master
+# Use this for testing changes to the nightly release process
+# Call with the CIRCLE_API_USER_TOKEN set to your Personal API key
+# You can find this under User Settings on Circle CI
+
+curl -u ${CIRCLE_API_USER_TOKEN}: \
+     -d build_parameters[CIRCLE_JOB]=nightly-build \
+     https://circleci.com/api/v1.1/project/github/wagtail/wagtail/tree/master