code: function setup() {
  	var build = null,
  		errors = '',
  		rootdir = path.resolve( __dirname, '..', '..' );
  
  	function spawnMake() {
  		debug( 'spawning %o', 'npm run build-css' );
  		build = spawn( 'npm', [ 'run', 'build-css' ], {
  			shell: true,
  			cwd: rootdir,
  			stdio: [ 'ignore', 'pipe', 'pipe' ],
  		} );
  		errors = '';
  		build.once( 'exit', onexit );
  		build.stdout.setEncoding( 'utf8' );
  		build.stdout.on( 'data', onstdout );
  		build.stderr.on( 'data', onstderr );
  	}
  
  	function onstdout( d ) {
  		debug( 'stdout %o', d.trim() );
  	}
  
  	function onexit() {
  		build.stderr.removeListener( 'data', onstderr );
  		build.stdout.removeListener( 'data', onstdout );
  		build = null;
  	}
  
  	function onstderr( stderr ) {
  		process.stderr.write( stderr.toString( 'utf8' ) );
  		errors += stderr.toString( 'utf8' );
  	}
  
  	return function( req, res, next ) {
  		if ( ! build ) {
  			spawnMake();
  		}
  
  		build.once( 'exit', function( code ) {
  			if ( 0 === code ) {
  				// `make` success
  				next();
  			} else {
  				// `make` failed
  				res.send( '<pre>`npm run build-css` failed \n\n' + errors + '</pre>' );
  			}
  		} );
  	};
  }
docs: Returns a "build middleware", which runs `npm run build-css` upon each HTTP
  request. Meant for use in "development" env.
  
  @return {Function} build middleware function
  @public