Adjust version matrix

We're only concerning ourselves with RHEL/Centos 6 so Ruby 1.8.7 and Ruby 1.9.3
will be the most likely versions. Due to a bug in rspec_puppet avoid Puppet
3.0.x. See rodjek/rspec-puppet#136

.travis.yml

@@ -6,14 +6,14 @@ rvm:
 script: bundle exec rake test
 env:
   matrix:
-  - PUPPET_VERSION="~> 3.1.0"
   - PUPPET_VERSION="~> 3.2.0"
-  - PUPPET_VERSION="~> 3.3.0"
+  - PUPPET_VERSION="~> 3.4.0"
+  - PUPPET_VERSION="~> 3.6.0"
 matrix:
   include:
-    - rvm: 2.0.0
-      env: PUPPET_VERSION="~> 3.3.0"
     - rvm: 1.8.7
       env: PUPPET_VERSION="~> 2.7.0"
     - rvm: 1.8.7
-      env: PUPPET_VERSION="~> 3.0.0"
+      env: PUPPET_VERSION="~> 3.4.0"
+    - rvm: 1.8.7
+      env: PUPPET_VERSION="~> 3.6.0"