add debian 7 tag and refactor url format

Author: chusiang

README.md

@@ -1,15 +1,21 @@
-# Docker image: Ansible on Jupyter
+# Docker image: Ansible on Jupyter Notebook
 
-A Docker image for run Ansible 2.2 on Jupyter 4.2 (ipython notebook).
+A Docker image for run [Ansible][ansible_offical] 2.2 on [Jupyter Notebook][jupyter_official] 4.2 (ipython notebook) with Browsers.
 
-- `alpine-3.4`, `latest` ([alpine/Dockerfile
-](https://github.com/chusiang/ansible-jupyter.dockerfile/blob/master/alpine/Dockerfile))
-- `debian-8` ([debian-8/Dockerfile
-](https://github.com/chusiang/ansible-jupyter.dockerfile/blob/master/debian-8/Dockerfile))
-- `ubuntu-14.04` ([ubuntu-14.04/Dockerfile
-](https://github.com/chusiang/ansible-jupyter.dockerfile/blob/master/ubuntu-14.04/Dockerfile))
-- `ubuntu-16.04` ([ubuntu-16.04/Dockerfile
-](https://github.com/chusiang/ansible-jupyter.dockerfile/blob/master/ubuntu-16.04/Dockerfile))
+[ansible_offical]:  https://www.ansible.com/
+[jupyter_official]: http://jupyter.org/
+
+- `alpine-3.4`, `latest` ([alpine/Dockerfile][dockerfile_alpine])
+- `debian-7` ([debian-7/Dockerfile][dockerfile_debian-7])
+- `debian-8` ([debian-8/Dockerfile][dockerfile_debian-8])
+- `ubuntu-14.04` ([ubuntu-14.04/Dockerfile][dockerfile_ubuntu-14.04])
+- `ubuntu-16.04` ([ubuntu-16.04/Dockerfile][dockerfile_ubuntu-16.04])
+
+[dockerfile_alpine]:        https://github.com/chusiang/ansible-jupyter.dockerfile/blob/master/alpine/Dockerfile
+[dockerfile_debian-7]:      https://github.com/chusiang/ansible-jupyter.dockerfile/blob/master/debian-7/Dockerfile
+[dockerfile_debian-8]:      https://github.com/chusiang/ansible-jupyter.dockerfile/blob/master/debian-8/Dockerfile
+[dockerfile_ubuntu-14.04]:  https://github.com/chusiang/ansible-jupyter.dockerfile/blob/master/ubuntu-14.04/Dockerfile
+[dockerfile_ubuntu-16.04]:  https://github.com/chusiang/ansible-jupyter.dockerfile/blob/master/ubuntu-16.04/Dockerfile
 
 ## Build image
 
@@ -75,14 +81,19 @@ Now, you can play the Ansible on Jupyter.
     $ open http://localhost:32786
     ```
     
-    ![2016-11-20-ansible-jupyter1](https://cloud.githubusercontent.com/assets/219066/20463322/218f0c4a-af6b-11e6-9a95-2411ec7acb5f.png)
+    ![2016-11-20-ansible-jupyter1]
+
+[2016-11-20-ansible-jupyter1]: https://cloud.githubusercontent.com/assets/219066/20463322/218f0c4a-af6b-11e6-9a95-2411ec7acb5f.png
+
+1. Attach my example ==> [`ansible_on_jupyter.ipynb`][ansible_on_jupyter.ipynb].
 
+[ansible_on_jupyter.ipynb]: https://github.com/chusiang/ansible-jupyter.dockerfile/blob/master/ipynb/ansible_on_jupyter.ipynb
 
-1. Attach my example ==> [`ansible_on_jupyter.ipynb`
-](https://github.com/chusiang/ansible-jupyter.dockerfile/blob/master/ipynb/ansible_on_jupyter.ipynb).
+    ![2016-11-20-ansible-jupyter2]
 
-    ![2016-11-20-ansible-jupyter](https://cloud.githubusercontent.com/assets/219066/20463319/fa8c047c-af6a-11e6-96d6-f985096c9c8c.png)
+[2016-11-20-ansible-jupyter2]: https://cloud.githubusercontent.com/assets/219066/20463319/fa8c047c-af6a-11e6-96d6-f985096c9c8c.png
 
-1. Remember use the `!` prefix to trigger command.
+1. Remember use the `!` prefix to trigger system command.
 
-Enjoy it ! 
+Enjoy it !
+I