SQUASH: review fixes
SQUASH: move to async-wrap.h and async-wrap-inl.h
tls_wrap: revert async_wrap support

Since crypto uses ObjectWrap it's difficult to get things working
properly. So going to punt on this for now and revisit when other
internals are more solid.
SQUASH: move request object to AsyncWrap

The request object itself is now part of AsyncWrap. This also means
removal of TLS and ZLib, since they both use ObjectWrap.