增加命令行主题参数

@@ -14,8 +14,8 @@ program
     .command('export <markdown_file> [html_file]')
     .alias('e')
     .description('export markdown to html')
-    .option('-A --abstract', 'abstract to current path')
-    .action(function (md, html) {
+    .option('-T --theme [theme_name]', 'css theme for html')
+    .action(function (md, html, options) {
         //判断目标输出参数
         if (!fs.existsSync(md)) {
             console.error(chalk.red(md + ' is not found'));
@@ -33,7 +33,8 @@ program
         fs.ensureFileSync(output);
 
         const viewer = new (require('../lib/view-markdown'))(process.cwd(), {inline: true});
-        let result = viewer.render(md, 'metro-lake');
+        let theme = options.theme || 'news';
+        let result = viewer.render(md, theme);
 
         fs.writeFile(output, result);
         console.log('html is exported to', chalk.green(output))