Make style generation module more loosely coupled by only caring about tags and class definitions

src/parser/generate-style.js

@@ -1,15 +1,15 @@
 'use strict';
 
-module.exports = function generateItemStyle(item, options) {
+module.exports = function generateItemStyle(tags, classes) {
-	let style = Object.assign({}, options.defaultStyle);
+	let style = {};
 
-	item.tags.forEach((tag) => {
+	tags.forEach((tag) => {
 		if (tag.type === "class") {
 			tag.classNames.forEach((className) => {
-				if (options.classes[className] == null) {
+				if (classes[className] == null) {
 					throw new Error(`Encountered unrecognized class ${className} in text`);
 				} else {
-					Object.assign(style, options.classes[className]);
+					Object.assign(style, classes[className]);
 				}
 			});
 		}