Manifest to install Opsmatic agent

The way to use the new class to install Opsmatic agent is:

    class { 'opsmatic::agent':
        token => $token,
        credentials => $debian_credentials,
    }

Stylistically, I prefer to align all the ='s just like you would align the =>'s below. See https://github.com/Nextdoor/puppet_rightscale/blob/master/manifests/repos.pp#L51-L56 for an example of how we align all of our variables.