Fix #34: check for state error onPreResponse.

If hapi detects a problem with state, e.g. if cookie decryption fails,
the onPreAuth handler will be skipped and request.session will remain
unset. Check if the session exists before handling it.
Merge pull request #36 from reid/check-state-error

Fix #34: check for state error onPreResponse.
Update package.json
Initial Hapi 6 update
Merge pull request #40 from jaw187/master

Initial Hapi 6 update
update version
2.3.2
Merge