Composer support string

[glaubinix]

Fixes getComposerInformation call if support is not an array but instead a string for example:

{"name": "acme/package", "support": "https://github.com/org/repo"}

Error

    "exception": {
        "class": "TypeError",
        "message": "Cannot access offset of type string on string",
        "code": 0,
        "file": "src\/Composer\/Repository\/Vcs\/GitHubDriver.php:179",
        "trace": [
            "src\/Composer\/Repository\/VcsRepository.php:248",

[Seldaek]

Thanks!