[AUTOMATED] Update Version Pinning for Terraform to support 0.13 (cloudposse#74)

## What

1. Update Version Pinning for Terraform to support 0.13

## Why

1. This is a relatively minor update that the CloudPosse module already likely supports.
1. This allows module consumers to not individually update our Terraform module to support Terraform 0.13.

Author: Gowiem

README.md

@@ -150,7 +150,7 @@ Available targets:
 
 | Name | Version |
 |------|---------|
-| terraform | ~> 0.12.0 |
+| terraform | >= 0.12.0, < 0.14.0 |
 | aws | ~> 2.0 |
 | null | ~> 2.0 |
 
@@ -299,22 +299,24 @@ Copyright © 2017-2020 [Cloud Posse, LLC](https://cpco.io/copyright)
 
 See [LICENSE](LICENSE) for full details.
 
-    Licensed to the Apache Software Foundation (ASF) under one
-    or more contributor license agreements.  See the NOTICE file
-    distributed with this work for additional information
-    regarding copyright ownership.  The ASF licenses this file
-    to you under the Apache License, Version 2.0 (the
-    "License"); you may not use this file except in compliance
-    with the License.  You may obtain a copy of the License at
-
-      https://www.apache.org/licenses/LICENSE-2.0
-
-    Unless required by applicable law or agreed to in writing,
-    software distributed under the License is distributed on an
-    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
-    KIND, either express or implied.  See the License for the
-    specific language governing permissions and limitations
-    under the License.
+```text
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  https://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+```
 
 
 

docs/terraform.md

@@ -2,7 +2,7 @@
 
 | Name | Version |
 |------|---------|
-| terraform | ~> 0.12.0 |
+| terraform | >= 0.12.0, < 0.14.0 |
 | aws | ~> 2.0 |
 | null | ~> 2.0 |
 

versions.tf

@@ -1,5 +1,5 @@
 terraform {
-  required_version = "~> 0.12.0"
+  required_version = ">= 0.12.0, < 0.14.0"
 
   required_providers {
     aws  = "~> 2.0"