Introducing changes in tags in nginx official docker images

latest: based on debian 8 jessie with a current build from mainline
branch  (stays the same as it was)

stable: based on debian 8 jessie with a current build from stable branch

mainline-alpine:: based on alpine:latest with a current build from
mainline branch

stable-alpine: based on alpine:latest with a current build from stable
branch

alpine: based on alpine:latest with a current build from mainline branch

library/nginx

@@ -1,6 +1,14 @@
 # maintainer: NGINX Docker Maintainers <[email protected]> (@nginxinc)
 
-latest: git://github.com/nginxinc/docker-nginx@e82e776e7507868a887178bc7eaae5c1ed7aa47f
-1: git://github.com/nginxinc/docker-nginx@e82e776e7507868a887178bc7eaae5c1ed7aa47f
-1.9: git://github.com/nginxinc/docker-nginx@e82e776e7507868a887178bc7eaae5c1ed7aa47f
-1.9.11: git://github.com/nginxinc/docker-nginx@e82e776e7507868a887178bc7eaae5c1ed7aa47f
+latest: git://github.com/nginxinc/docker-nginx@f48d943038eaafd1f69cb14d86db95b3044bd4d8 mainline/jessie
+1: git://github.com/nginxinc/docker-nginx@f48d943038eaafd1f69cb14d86db95b3044bd4d8 mainline/jessie
+1.9: git://github.com/nginxinc/docker-nginx@f48d943038eaafd1f69cb14d86db95b3044bd4d8 mainline/jessie
+1.9.12: git://github.com/nginxinc/docker-nginx@f48d943038eaafd1f69cb14d86db95b3044bd4d8 mainline/jessie
+
+stable: git://github.com/nginxinc/docker-nginx@14c1b938737cf4399a6bb039bc506957dce562ae stable/jessie
+1.8: git://github.com/nginxinc/docker-nginx@14c1b938737cf4399a6bb039bc506957dce562ae stable/jessie
+1.8.1: git://github.com/nginxinc/docker-nginx@14c1b938737cf4399a6bb039bc506957dce562ae stable/jessie
+
+stable-alpine: git://github.com/nginxinc/docker-nginx@14c1b938737cf4399a6bb039bc506957dce562ae stable/alpine
+mainline-alpine: git://github.com/nginxinc/docker-nginx@14c1b938737cf4399a6bb039bc506957dce562ae mainline/alpine
+alpine: git://github.com/nginxinc/docker-nginx@14c1b938737cf4399a6bb039bc506957dce562ae mainline/alpine