Add a CONTRIBUTING document

Tim Visher · Tim Visher · commit aa823abb5728 · 2018-02-22T11:04:12.000-05:00
Motivation
----------

This should be the place to document the process for submitting changes
to singer-python.
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
@@ -0,0 +1,8 @@
+# How to Contribute
+
+## Submitting a PR
+
+1. Please make sure that all tests pass and that the code passes linting
+   with `make`.
+
+1. Open up the PR.
