update terraform module readme

Author: mdevilliers

terraform/modules/lamda-deployer/readme.md

@@ -1,11 +1,13 @@
 ## Inputs
 
-| Name | Description | Type | Default | Required |
-|------|-------------|:----:|:-----:|:-----:|
-| application | The name of the application | string | - | yes |
-| deployer_filepath | File path to a zip file containing the deployer | string | - | yes |
-| env_vars | A map of variables to be passed to the lambda function on deployment | map | `<map>` | no |
-| environment | The name of the environment | string | - | yes |
-| function_role_arn | The arn of the role the function will be deployed with | string | - | yes |
-| s3_bucket_arn | The arn of the S3 bucket to use for uploading applications from CI | string | - | yes |
-| s3_bucket_id | The id of the S3 bucket to use for uploading applications from CI | string | - | yes |
+| Name                       | Description                                                                                     | Type   | Default | Required |
+| ------                     | -------------                                                                                   | :----: | :-----: | :-----:  |
+| application                | The name of the application                                                                     | string | -       | yes      |
+| deployer_filepath          | File path to a zip file containing the deployer                                                 | string | -       | yes      |
+| env_vars                   | A map of variables to be passed to the lambda function on deployment                            | map    | `<map>` | no       |
+| environment                | The name of the environment                                                                     | string | -       | yes      |
+| function_role_arn          | The arn of the role the function will be deployed with                                          | string | -       | yes      |
+| maximum_unaliased_versions | The number of versions without an alias to keep. A function with an alias is a function in use. | string | `3`     | no       |
+| s3_bucket_arn              | The arn of the S3 bucket to use for uploading applications from CI                              | string | -       | yes      |
+| s3_bucket_id               | The id of the S3 bucket to use for uploading applications from CI                               | string | -       | yes      |
+