Code: Improves outFile condition.
Code: Moves temp return after the condition.
So manual build can kick in.
Binding: Passes ctx_w pointer to helpers.
* Pushes NanDisposePersistent to very end.
Code: Caches result as soon as v8 returns.
Not fixes segfault bug, but brings clarity of intent.
Merge pull request #584 from am11/master

Misc. fixes
README: Updates example with missing error info.