Support for transport pipe configuration

With Sensu 0.13, the transport option was added, replacing the aqmp option. This pull request allows the transport option to be configured, including the option array. See example below.

```
puppet configuration:
  sensu::handler { 'graphite':
    type     => 'transport',
    pipe     => {
      type    => 'topic',
      name    => 'metrics',
      options => {
        durable => 'true',
        passive => 'true',
      },
    },
    mutator  => 'only_check_output',
  }

Results in sensu handler configuration:
{
  "handlers": {
    "graphite": {
      "type": "transport",
      "pipe": {
        "options": {
          "passive": "true",
          "durable": "true"
        },
        "type": "topic",
        "name": "metrics"
      },
      "mutator": "only_check_output",
    }
  }
}
```