Add contributing guidelines

Author: kswedberg

readme.md

@@ -152,3 +152,11 @@ these methods return a jQuery object containing an empty array, just like
 all of jQuery's other DOM traversal methods. Any further chained methods,
 therefore, will be called against no elements (which, in most cases,
 means that nothing will happen).
+
+## Contributing
+
+Thank you! Please consider the following when working on this repo before you submit a pull request:
+
+* For code changes, please work on the "source" file: `src/jquery.smooth-scroll.js`.
+* Style conventions are noted in the `jshint` grunt file options and the `.jscsrc` file. To be sure your additions comply, run `grunt lint` from the command line.
+* If possible, please use Tim Pope's [git commit message style](http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html). Multiple commits in a pull request will be squashed into a single commit. I may adjust the message for clarity, style, or grammar. I manually commit all merged PRs using the `--author` flag to ensure that proper authorship (yours) is maintained.