Propose to add bare README explaining how to contribute

README

+This is gdat
+
+More information will follow here
+
+git-hosted version currently under development for automated tests etc.
+
+## Policy for contributing
+* `master` branch is protected, changes can only be made via merge requests.
+* To propose changes:
+ * Open an issue to discuss the matter
+ * Then open a branch to work on the issue
+ * When done, submit a merge request to the master branch.