Update Terraform.gitignore

Improvements: 

 * `.terraform` directories could be created in any subdirectory when user runs `terraform init`.
 * Quite an interesting variations of`.tfstate` files are created by Terraform such as `.*.tfstate.d` or  `.*.tfstate.lock.info`. It's best not to name any file with `*.tfstate.*` pattern.
 * `*.tfvars` files often contain private data and not supposed to be committed.

Terraform.gitignore

-# Compiled files
-*.tfstate
-*.tfstate.*.backup
-*.tfstate.backup
+#  Local .terraform directories
+**/.terraform/*
 
-# Module directory
-.terraform/
+# .tfstate files
+*.tfstate
+*.tfstate.*
 
-# Variable values for development
-terraform.tfvars
+# .tfvars files
+*.tfvars