Merge pull request mathjax#182 from mathjax/issue172

Make test for node hierarchy more robust.

Author: dpvc

lib/patch/jsdom.js

@@ -3,12 +3,8 @@
 //  between node 4 and node 5, so check which one we have.
 //
 
-var fs = require('fs');
-
-var PARSERS = 'jsdom/node_modules/cssstyle/lib/parsers.js';  // node 4 hierarchy
-try {fs.accessSync('node_modules/'+PARSERS, fs.F_OK)} catch (e) {
-  PARSERS = 'cssstyle/lib/parsers.js';  // node 5 heirarchy
-}
+var PARSERS = 'jsdom/node_modules/cssstyle/lib/parsers.js';             // node 4 hierarchy
+try {require(PARSERS)} catch (e) {PARSERS = 'cssstyle/lib/parsers.js'}  // node 5 heirarchy
 
 //
 //  Companion to implicitSetter, but for the individual parts.