function followers( opts, clbk ) {
	factory( opts, clbk )();
}
Gets a user's followers.

@param {Object} opts - function options
@param {string} [opts.token] - GitHub access token
@param {string} [opts.username] - GitHub username
@param {string} [opts.useragent] - user agent string
@param {Function} clbk - callback to invoke upon query completion
@returns {void}