Update the readme to point to 0.7.0 as the latest stable version

Docker-DCO-1.1-Signed-off-by: Mangled Deutz <[email protected]> (github: dmp42)

Author: Mangled Deutz

README.md

@@ -11,7 +11,7 @@ As the documentation evolves with different registry versions, be sure that befo
  * check which version of the registry you are running
  * switch to the corresponding tag to access the README that matches your product version
 
-The stable, released version is currently the [0.6.9 tag](https://github.com/dotcloud/docker-registry/tree/0.6.9).
+The stable, released version is currently the [0.7.0 tag](https://github.com/dotcloud/docker-registry/tree/0.7.0).
 
 
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