docs(github): simplify pull request template (#853)

We've found that half of the engineering team either hates or doesn't even bother using the PR
templates. Refactoring it down to the bare minimum should suffice.

Author: Matthew Fisher

.github/PULL_REQUEST_TEMPLATE

@@ -1,52 +1,8 @@
-# Summary of Changes
-
-Please explain what this PR changes, and include what unit tests you've written (we hope you wrote tests!)
-
-# Issue(s) that this PR Closes
-
-Please list the issue(s) that this PR closes, similar to the below:
-
-closes #1234
-closes #5678
-
-# Associated [End To End Test](https://github.com/deis/workflow-e2e) PR(s)
-
-If your change requires any additions or changes to the [end to end tests](https://github.com/deis/workflow-e2e), please submit them as 1 or more pull requests against that repo and refer to them here.
-
-refs deis/workflow-e2e#1234
-refs deis/workflow-e2e#5678
-
-# Associated [Documentation](https://github.com/deis/workflow) PR(s)
-
-If your change requires any additions or changes to the [official documentation](https://github.com/deis/workflow), please submit them as 1 or more pull requests against that repo and refer to them here.
+If your change requires any additions or changes to the [documentation][docs] or to the [end-to-end test suite][e2e], please submit them as 1 or more pull requests against that repo and refer to them here.
 
 refs deis/workflow#1234
-refs deis/workflow#5678
-
-# Associated [Design Document](http://docs.deis.io/en/latest/contributing/design-documents)(s)
-
-If your change was inspired by 1 or more design document(s), please provide a list of links to them here.
-
-# Testing Instructions
-
-Please provide a detailed list for how to test the changes in this PR.
-
-1. Create a Deis Cluster
-2. Register an app
-3. Your steps here
-
-Also, please provide a description of the desired result after the tester completes the above steps.
-
-1. The app called "abcd" should be deployed
-2. `kubectl get pod --namespace=abcd` should show 2 pods running
-3. etc.
-
-# Pull Request Hygiene TODOs
-
-Please make sure the below checklist is complete.
+refs deis/workflow-e2e#5678
 
-- [ ] Your pull request is concise and to the point (make another PR for refactoring nearby code)
-- [ ] Your commits are squashed into logical units of work
-- [ ] Your commits follow the [commit style guidelines](http://docs.deis.io/en/latest/contributing/standards/#commit-style-guide)
 
-:cherry_blossom: Thank you! :cherry_blossom:
+[docs]: https://github.com/deis/workflow
+[e2e]: https://github.com/deis/workflow-e2e