Add towncrier for CHANGELOG management

Fix #154

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,17 @@
+Thanks for submitting a PR, your contribution is really appreciated!
+
+Here's a quick checklist that should be present in PRs:
+
+- [ ] Make sure to include reasonable tests for your change if necessary
+
+- [ ] Add a new news fragment into the changelog folder, following these guidelines:
+  * Name it `$issue_id.$type` for example `588.bug`
+  * If you don't have an issue_id change it to the PR id after creating it
+  * Ensure type is one of `removal`, `feature`, `bugfix`, `vendor`, `doc` or `trivial`
+  * Make sure to use full sentences with correct case and punctuation, for example:
+
+    ```
+    Fix issue with non-ascii contents in doctest text files.
+    ```
+
+