Added composer.json

You love composer.
I love composer.
We all love composer.

Toxid is now installable using:

    {
        "repositories": [
          { "type": "vcs", "url":  "https://github.com/jkrug/TOXID-cURL.git" }
        ],

        "require": {
          "jkrug/toxid_curl": "dev-master"
        },

        "extra": {
          "installer-paths": {
            "shop/modules/toxid_curl": ["jkrug/toxid_curl"],
          }
    }