Merge pull request #38 from terraform-google-modules/document-gcloud

Add gcloud dependency info

README.md

@@ -133,9 +133,10 @@ The routes list contains maps, where each object represents a route. For the nex
 | priority | The priority of this route. Priority is used to break ties in cases where there is more than one matching route of equal prefix length. In the case of two routes with equal prefix length, the one with the lowest-numbered priority value wins | string | 1000 | yes |
 
 ## Requirements
-### Terraform plugins
+### Installed Software
 - [Terraform](https://www.terraform.io/downloads.html) 0.10.x
 - [terraform-provider-google](https://github.com/terraform-providers/terraform-provider-google) plugin v1.12.0
+- [gcloud](https://cloud.google.com/sdk/gcloud/) >243.0.0
 
 ### Configure a Service Account
 In order to execute this module you must have a Service Account with the following roles: