Support Puppet v4

The CHANGELOG states that Puppet v4 support is present, though without
this patch the metadata does not reflect that nor is there testing with
Travis-ci.

.travis.yml

@@ -16,10 +16,14 @@ env:
   - PUPPET_GEM_VERSION="~> 3.7"
   - PUPPET_GEM_VERSION="~> 3"
   - PUPPET_GEM_VERSION="~> 3" PARSER="future"
+  - PUPPET_GEM_VERSION="~> 4"
   global:
   - PUBLISHER_LOGIN=puppetlabs
   -  secure: "FInoEwh3G4Auqp+OOdIc20lDLqrV6FHzWsM8ercHWjhDRD23VI49B1qqehWjaI8lKM3D5mTvdup23IVQBJo8M0rR/yfju1NhMYFTQ5bcJIrbQ3fn4n/zSaE8gLTOtHwzjSlqTJAYjxOAnp1VdMZngqpU/RYfSk68zJD34NqfovA="
 matrix:
   fast_finish: true
+  exclude:
+    - rvm: 1.8.7
+      env: PUPPET_GEM_VERSION="~> 4"
 notifications:
   email: false

metadata.json

@@ -67,7 +67,7 @@
     "requirements": [
     {
       "name": "puppet",
-      "version_requirement": ">=3.7.1 <4.0.0"
+      "version_requirement": ">=3.7.1 <5.0.0"
     }
     ],