Update readme

Master branch is no longer subject to rebases.
Also, update links.

README.md

@@ -1,10 +1,9 @@
 Qubes core, version 3
 ---------------------
 
-[![Build Status](https://travis-ci.org/woju/qubes-core-admin.svg?branch=core3-devel)](https://travis-ci.org/woju/qubes-core-admin)
+[![Build Status](https://travis-ci.org/QubesOS/qubes-core-admin.svg?branch=master)](https://travis-ci.org/QubesOS/qubes-core-admin)
 <img src="https://readthedocs.org/projects/qubes-core-admin/badge/?version=latest">
 
-This is development branch of the Qubes OS core. This branch is subject to
-rebase without warning until further notice.
+This is master branch of the Qubes OS core.
 
-API documentation is available: https://qubes-core-admin.readthedocs.org/en/latest/.
+API documentation is available: https://dev.qubes-os.org/projects/core-admin/en/latest/.