Upgrade docker-machine default version to 0.16

Author: npalm

CHANGELOG.md

@@ -5,7 +5,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
-
+- Changed: Updated default docker-machine version to 0.16.0
+- Changed: Updated default gitlab runner to 11.6.0
 - Added: Configuration parameters for post_build_script, pre_clone_script, request_concurrency and output_limit. #22
 - Added: Configurable docker image for runner #27
 - Added: Add pre/post install user-data snippets for runners #26

variables.tf

@@ -73,7 +73,7 @@ variable "docker_machine_spot_price_bid" {
 
 variable "docker_machine_version" {
   description = "Version of docker-machine."
-  default     = "0.15.0"
+  default     = "0.16.0"
 }
 
 variable "runners_name" {
@@ -231,7 +231,7 @@ variable "cache_expiration_days" {
 variable "gitlab_runner_version" {
   description = "Version for the gitlab runner."
   type        = "string"
-  default     = "11.3.1"
+  default     = "11.6.0"
 }
 
 variable "enable_cloudwatch_logging" {