Revert "Document branch structure and release method."

This repository has switched from a `develop=edge,master=stable` to
a `master=edge,stable=stable` structure.

This reverts commit 3d4957bf0ce46ec3530ef46cc77f96dc38c92c37.
Update README build status to master,stable .

This repository has switched from a `develop=edge,master=stable` to
a `master=edge,stable=stable` structure.