Merge pull request #525 from prometheus/grobie/pr-template-for-output-repo

Add template to redirect people to docs repo for changes

Makefile

@@ -22,6 +22,8 @@ downloads/%/releases.json:
 
 github_pages_export: compile
 	cd output && \
+		mkdir -p .github && \
+		echo "This repository is auto-generated. You have to open pull requests against https://github.com/prometheus/docs instead." > .github/PULL_REQUEST_TEMPLATE.md && \
 		echo prometheus.io > CNAME && \
 		git init && \
 		git config user.name "Travis CI" && \