[Feature request] Support alternate install filenames on Darwin

[williamtheaker]

Package names are currently hardcoded, which requires patching go2chef to use it with a free/libre Chef distribution like Cinc. Allowing passing arbitrary filenames would make this tool more broadly useful if someone wants to use it as go2puppet or such.

[williamtheaker]

I reread the config file example in the README a few more times and realized this is already possible:

{
  "steps": [
    {
      "type": "go2chef.step.install.darwin.pkg",
      "name": "Download and install Cinc",
      "is_dmg": true,
      "pkg_match": "cinc.*",
      "dmg_match": "cinc.*",
      "source": {
        "type": "go2chef.source.http",
        "sha256": "07cebb59431a8c491084e3ccd1b8fde52aa10f970a45ce865ecc19cc5f690a81",
        "url": "http://downloads.cinc.sh/files/stable/cinc/17.8.25/mac_os_x/11/cinc-17.8.25-1.x86_64.dmg"
      }
    }
  ]
}

Maybe I should open a separate issue about putting the undocumented config keys in the README or elsewhere?