updated the mustache file for issue #25 and PR #26

Author: mhamzak008

templates/common_README.mustache

@@ -19,6 +19,11 @@ except ApiException as e:
     print("Exception when calling {{classname}}->{{operationId}}: %s\n" % e)
 {{/-first}}{{/operation}}{{/operations}}{{/-first}}{{/apis}}{{/apiInfo}}
 ```
+Note: if you have an european account please set attribute 'host'
+
+```
+configuration.host = 'https://api.eu.opsgenie.com'
+```
 
 ## Documentation for API Endpoints