Invalid Parameter lts

Hi, I've simplified the last couple of pull requests you've had for this issue, in the hope that it builds and you can merge it.

Running this config:

```ruby
jenkins: {
      class { 'jenkins':
        repo    => 1,
        version => 'latest',
      }
}
```

Currently renders this error:

```ruby
Error: Could not retrieve catalog from remote server: Error 400 on SERVER: Invalid parameter lts at /home/acaire/code/puppet-cloud/modules/jenkins/manifests/repo.pp:28 on node
```

Adding the parameter alone fixes it, at least in Puppet 3.1.1.