Add support for hash_behaviour=merge to atk-show-vars

[andyrhee]

We use hash_behaviour=merge (e.g. in ansible.cfg) in our roles heavy env. In this case, it would be helpful to show the resulting dictionary as additive instead of exclusive. For example, the show_diff function could display output showing previous items, new items, and merged items.

I can simply modify the show_diff function to suit my case, but it may be useful to other people to add this as an option.

--- /Library/Python/2.7/site-packages/ansible_toolkit/show_vars.py.orig 2016-02-26 16:59:12.000000000 -0800
+++ /Library/Python/2.7/site-packages/ansible_toolkit/show_vars.py  2016-02-26 17:07:33.000000000 -0800
@@ -9,8 +9,15 @@
         if k in old.keys() and v == old[k]:
             continue
         if k in old.keys() and v != old[k]:
-            red(" - ['{}'] = {}".format(k, old[k]))
-        green(" + ['{}'] = {}".format(k, v))
+            # as if hash_behaviour = merge
+            z = old[k].copy()
+            z.update(v)
+
+            green(" p ['{}'] = {}".format(k, old[k]))
+            red(" + ['{}'] = {}".format(k, v))
+            green(" = ['{}'] = {}".format(k, z))
+        else:
+            green(" + ['{}'] = {}".format(k, v))