add debian files, fist cut

CONTRIBUTING.md

@@ -0,0 +1,29 @@
+# Contributors guide
+
+## Packaging
+
+An unsigned Debian package can be created from the repository in a few steps.
+
+Check out the version you want:
+
+```bash
+VERSION=1.0
+git checkout v$VERSION
+```
+
+Write a 'pristine source' tarball from `git`:
+
+```bash
+git archive --format tar.gz HEAD --prefix mdcheckr-$VERSION/ mdcheckr tests README.md LICENSE.md > mdcheckr_$VERSION.orig.tar.gz
+```
+
+Extract, add the Debian goodies, compile, and cleanup:
+
+```bash
+tar -xzf mdcheckr_$VERSION.orig.tar.gz
+cp -Rf debian/ mdcheckr-$VERSION/
+(cd mdcheckr-$VERSION/ && debuild -us -uc)
+rm -Rf mdcheckr-$VERSION/
+```
+
+You will then have source and binary packages in the current directory.