Misc fixes

* Code: Improves outFile condition (b5b8ce6)
  * It should compute outFile when either `data` or `file` options are set.
* Code: Moves temp return after the condition. (7ef08f4)
  * So manual build can kick in.
* Binding: Passes ctx_w pointer to helpers. (df22805)
  * Pushes NanDisposePersistent to very end.
* Code: Caches result as soon as v8 returns. (a5067a6)
  * Not fixes segfault bug, but brings clarity of intent.