add a contributing file, based on pynucastrot

Author: zingale

CONTRIBUTING.md

@@ -0,0 +1,31 @@
+# Contributing
+
+Contributions are welcomed from anyone, including posting issues or
+submitting pull requests to the [pyro github](https://github.com/zingale/pyro).
+
+## Issues
+
+Creating an issue on github is a good way to request new features,
+file a bug report, or notify us of any difficulties that arise using
+pyro.
+
+To request support using pyro, please create an issue on the pyro
+github and the developers will be happy to assist you.
+
+If you are reporting a bug, please indicate any information necessary
+to reproduce the bug including your version of python.
+
+## Pull Requests
+
+*Any contributions that have the potential to change answers should be
+done via pull requests.* A pull request should be generated from your
+fork of pyro and target the `master` branch.
+
+The unit and regression tests will run automatically once the PR is
+submitted, and then one of the pyro developers will review the PR and
+if needed, suggest modifications prior to merging the PR.
+
+If there are a number of small commits making up the PR, we may wish
+to squash commits upon merge to have a clean history.  *Please ensure
+that your PR title and first post are descriptive, since these will be
+used for a squashed commit message.*