Added one more example in azure.md file (GoogleCloudPlatform#1155)

* Update azure_service.go

Added Duplicate check method to avoid error having same name in different Resource group or at sub level

* fixed duplicate issue

* fixed duplicate issue

* fixed duplicate resource for nsg

* fixed virtual network duplicate resource issue

* Update virtual_network.go

* Update azure.md

Added example to get details for specific Resource Group

docs/azure.md

@@ -23,8 +23,10 @@ export ARM_TENANT_ID=[TENANT_ID]
 
 ./terraformer import azure -r resource_group
 ./terraformer import azure -R my_resource_group -r virtual_network,resource_group
+./terraformer import azure -r resource_group --filter=resource_group=/subscriptions/<Subscription id>/resourceGroups/<RGNAME>
 ```
 
+
 ## List of supported Azure resources
 
 *   `analysis`