add blurb about linking to issues on commit and make markdown hyperlinks the same style as readme.me

contributing.md

@@ -1,21 +1,15 @@
 # Contributing
 
 We love pull requests from everyone. By participating in this project, you
-agree to abide by the Wagtail [code of conduct].
-
-[code of conduct]: https://github.com/wagtail/wagtail/blob/master/CODE_OF_CONDUCT.md
+agree to abide by the Wagtail [code of conduct](https://github.com/wagtail/wagtail/blob/master/CODE_OF_CONDUCT.md).
 
 If you do not have write access to the repo, fork, then clone the repo:
 
     git clone git@github.com:your-username/bakerydemo.git
 
-Set up your machine for [development]:
-
-[development]: https://github.com/wagtail/bakerydemo/blob/master/readme.md
+Set up your machine for [development](https://github.com/wagtail/bakerydemo/blob/master/readme.md).
 
-Push to your fork and [submit a pull request][pr].
-
-[pr]: https://github.com/wagtail/bakerydemo/compare/
+Push to your fork and [submit a pull request](https://github.com/wagtail/bakerydemo/compare/).
 
 For contributors that have write access, if you create a PR that is not
 ready for review, please assign the **work in progress** label to the PR. Once ready
@@ -25,6 +19,9 @@ label to the PR.
 Please use your best judgement if committing directly to master. All non-trivial development
 should be done on a branch.
 
+For all work, please cross reference and close issues in
+[commit messages](https://help.github.com/articles/closing-issues-via-commit-messages/)
+
 At this point you're waiting on us. We like to at least comment on pull requests
 within three business days (and, typically, one business day). We may suggest
 some changes or improvements or alternatives.