Instructions for when "vendor" access is disabled

[bshaffer]

For some cases, such as when a Heroku build pack is used, access to the vendor directory is disabled. This also may be a general best practice.

We should try for a fix and document the behavior. One option would be recommend installing vendor/bin to somewhere else:

# composer.json
{
    "config": {
        "bin-dir": "scripts"
    }
}

Another option would be to recommend copy/pasting the router.php into your project file instead of using ours. This requires more effort to get started, but may be a better / more secure solution.