Add requirements.txt file

This commit adds a requirements.txt file so we can ensure dependencies
are versioned instead of going for the latest available version.

Author: danielmellado

README.md

@@ -16,8 +16,7 @@ The resource module builder is an Ansible Playbook that helps developers scaffol
 ### Usage
 
 ```
-pip install ansible
-pip install jsonref
+pip install -r requirements.txt
 ```
 
 ```

requirements.txt

@@ -0,0 +1,6 @@
+# The order of packages is significant, because pip processes them in the order
+# of appearance. Changing the order has an impact on the overall integration
+# process, which may cause wedges in the gate later.
+
+ansible>=2.8.0 # GPLv3
+jsonref>=0.2  # MIT