function url( opts ) {
	var slug;
	var str;

	slug = opts.slug.split( '/' );
	slug = slug[ 0 ] + '/' + slug[ 1 ] + '@' + slug[ 2 ];

	str = '';
	str += opts.protocol+'://';
	str += opts.hostname+'/gh/';
	str += slug+'/';
	str += opts.file;
	return str;
}
Returns a jsDelivr URL.

@private
@param {Options} opts - function options
@param {string} opts.protocol - HTTP protocol
@param {string} opts.hostname - jsDelivr hostname
@param {string} opts.slug - repository slug
@param {string} opts.file - filepath
@returns {string} jsDelivr URL

@example
var out = url({
    'protocol': 'https',
    'hostname': 'cdn.jsdelivr.net',
    'slug': 'stdlib-js/stdlib/develop',
    'file': 'README.md'
});
// returns 'https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@develop/README.md'