Add Wordpress plugins to composer.json file, from custom Git-repo.

wp-plugin-composer.json

/** name: on the repo is what you call later down in the "require" section.
          It does not necessarily need to be the repo user and repo name, but is good practice! :) 
**/

{
  "repositories": [
    {
      "type": "composer",
      "url": "http://wpackagist.org"
    },
    {
      "type": "package",
      "package": {
        "name": "the-user/the-repo",
        "version": "1.3.4",
        "type": "wordpress-plugin",
        "dist": {
          "type": "zip",
          "url": "https://github.com/the-user/the-repo/archive/master.zip"
        },
        "require" : {
          "composer/installers": "v1.0.6"
        }
      }
    }
  ],
  "require": {
    "php": ">=5.3.0",
    "the-user/the-repo": "1.3.4"
  }
}