remove runtime from lib/babel

It brings polyfills and breaks tests for old Node.js

Author: floatdrop

lib/babel.js

@@ -16,7 +16,7 @@ try {
 
 var options = {
 	blacklist: hasGenerators ? ['regenerator'] : [],
-	optional: hasGenerators ? ['asyncToGenerator', 'runtime'] : ['runtime'],
+	optional: hasGenerators ? ['asyncToGenerator'] : [],
 	plugins: [
 		createEspowerPlugin(babel, {
 			patterns: require('./enhance-assert').PATTERNS