Initial PR template.

.github/PULL_REQUEST_TEMPLATE

@@ -0,0 +1,11 @@
+## Remove this paragraph
+
+Please have a look at our developer documentation before submitting your Pull Request.
+
+https://twistedmatrix.com/trac/wiki/TwistedDevelopment#SubmittingaPatch
+
+## Contributor Checklist:
+
+* [ ] There is an associated ticket in Trac. Create a new one at https://twistedmatrix.com/trac/newticket
+* [ ] I have created a newsfragment in src/twisted/newsfragments/ (see: https://twistedmatrix.com/trac/wiki/ReviewProcess#Newsfiles )
+* [ ] I have updated the automated tests.

CONTRIBUTING

@@ -15,8 +15,6 @@ https://twistedmatrix.com/trac/wiki/ContributingToTwistedLabs
 
 Twisted has a Code of Conduct, available at code_of_conduct.md.
 
-**Warning: pull requests are ignored** unless they have an associated ticket in trac.
-
 File a ticket at:
 
 https://twistedmatrix.com/trac/newticket
@@ -24,6 +22,7 @@ https://twistedmatrix.com/trac/newticket
 Twisted uses Trac to keep track of bugs, feature requests, and associated
 patches because GitHub doesn't provide adequate tooling for its community.
 
+Contributions are managed using GitHub's Pull Requests.
 For a PR to be accepted it needs to have:
 
 * all Travis CI tests passing