Support commands with options in play plugin

This adds support for specifying additional options in the command config value for the play plugin. Example:

```
play:
    command: /usr/bin/command --option1 --option2 some_other_option
```

The motivation for this is to make it work with the command-line client for [ghedo/grooved](https://github.com/ghedo/grooved), but I imagine it could be useful for other people too.