Fix autoload path for case sensitive operating systems

PHP generates a fatal error from Composer's autoload for OS's with case sensitive paths, due to the path being Titlecased: 

     src/Crossjoin/Browscap

but the composer.json autoload being lowercase:

    "autoload": {
        "psr-4": {
            "Crossjoin\\Browscap\\": "src/crossjoin/browscap/"
        }
    }

This simply fixes the path in composer.json.