Closes #55, make api version used in responses dynamic

ec2stack/helpers.py

diff --git a/ec2stack/helpers.py b/ec2stack/helpers.py
index 1ad5467..57dc655 100644
--- a/ec2stack/helpers.py
+++ b/ec2stack/helpers.py
@@ -309,7 +309,8 @@
     @param kwargs: Parameters to render the template with.
     @return: Response.
     """
-    content = render_template(request_id=uuid(), **kwargs)
+    api_version = str(get("Version"))
+    content = render_template(request_id=uuid(), api_version=api_version, **kwargs)
     response = make_response(content)
     return _create_response(response, '200')
 

ec2stack/providers/cloudstack/tags.py

diff --git a/ec2stack/providers/cloudstack/tags.py b/ec2stack/providers/cloudstack/tags.py
index dedea27..40a1100 100644
--- a/ec2stack/providers/cloudstack/tags.py
+++ b/ec2stack/providers/cloudstack/tags.py
@@ -148,5 +148,5 @@
     return {
         'template_name_or_list': 'tags.xml',
         'response_type': 'DescribeTagsResponse',
-        'response': response
+        'response': response['listtagsresponse']
     }

ec2stack/templates/response.xml

diff --git a/ec2stack/templates/response.xml b/ec2stack/templates/response.xml
index ea170ca..3b8dcde 100644
--- a/ec2stack/templates/response.xml
+++ b/ec2stack/templates/response.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<{{response_type}}{% if not error %} xmlns="http://ec2.amazonaws.com/doc/2014-05-01/"{%endif%}>
+<{{response_type}}{% if not error %} xmlns="http://ec2.amazonaws.com/doc/{{api_version}}/"{%endif%}>
     {% block response_content %}{% endblock %}
     {% if request_id %}
     <RequestId>{{request_id}}</RequestId>