Merge pull request #83 from Foxhind/fix/clean-xpi-temp-dir

use remove method instead of unlink

lib/firefox_profile.js

@@ -151,7 +151,7 @@ function FirefoxProfile(options) {
 
 function deleteParallel(files, cb) {
   async.parallel(files.map(function(file) {
-    return function(next) { fs.unlink(file, next); };
+    return function(next) { fs.remove(file, next); };
   }), function () {
     cb && cb();
   });