Support for passing args

I'm running a martini server using fresh and I need to pass some command line args to my program, but can't find any support for it. 

It would be great with either a command line switch for the `fresh` command:

```
fresh -a "--my-custom-arg=123 --and-another=true"
```

... or an option in the config file:

```
args: --my-custom-arg=123 --and-another=true
```

Perhaps both? 
