[FEATURE] add main sass file

app/index.js

@@ -131,7 +131,14 @@ module.exports = yeoman.generators.Base.extend((function() {
 			answers
 		);
 	};
-	
+
+	Generator.writeSass = function() {
+		this.fs.copy(
+			this.templatePath('_main.scss'),
+			this.destinationPath(answers.sassPath + '/main.scss')
+		);
+	};
+
 	Generator.writeDependencyManagement = function() {
 		this.fs.copyTpl(
 			this.templatePath('_package.json'),