update stdlib requirement to release 4.0.0

stdlib versions prior to 4.0.0 do not support passing booleans to
str2bool and cause failures.

Author: Aaron Russo

.fixtures.yml

@@ -7,4 +7,4 @@ fixtures:
       ref: "0.0.7"
     "stdlib":
       repo: "git://github.com/puppetlabs/puppetlabs-stdlib.git"
-      ref: "2.6.0"
+      ref: "4.0.0"

Modulefile

@@ -5,4 +5,4 @@ description "stunnel management module with support for multiple tunnels, init
  scripts and both server/client tunnels"
 project_page "https://github.com/arusso/puppet-stunnel"
 license "MIT License"
-dependency 'puppetlabs/stdlib', '>= 2.6.0'
+dependency 'puppetlabs/stdlib', '>= 4.0.0'