style(README): format code excerpt

Author: stephanebachelier

README.md

@@ -299,10 +299,13 @@ For example:
 'useminPrepare', {
     options: {
         resolveSource: function (sourceUrl, fileDir, fileName, blockTarget, searchPath) {
-            var fs = require('fs'), path = require('path');
-            for (var i=0; i< searchPath.length; ++i) {
+            var fs = require('fs');
+            var path = require('path');
+            for (var i=0; i < searchPath.length; ++i) {
               var source = path.join(searchPath[i], fname);
-              if (fs.existsSync(source)) { return source; }
+              if (fs.existsSync(source)) {
+                return source;
+              }
             }
             return false;
         }