fixed problem creating node storage directory

oauth3.node.storage.js

@@ -9,6 +9,11 @@ var sessionsdir = path.join(oauth3dir, 'sessions');
 var directivesdir = path.join(oauth3dir, 'directives');
 var metadir = path.join(oauth3dir, 'meta');
 
+// We can reasonably assume the existence of the home directory, but we can't assume
+// that there will already be a `.oauth3` directory or anything inside of it.
+if (!fs.existsSync(path.join(oauth3dir, '..'))) {
+  fs.mkdirSync(path.join(oauth3dir, '..'));
+}
 if (!fs.existsSync(oauth3dir)) {
   fs.mkdirSync(oauth3dir);
 }