Invalid const for MSG_REJECT_REQUEUE

[FreekGille]

Hi again!

I was tinkering with some reject messages and noticed the following error:

Undefined class constant 'MSG_REJECT_REQUEUE'

This MSG_REJECT_REQUEUE is documented in the readme. When investigating, I came came across ConsumerInterface.php which has three constants, MSG_ACK, MSG_REJECT and MSG_REQUEUE.
Bug seems to be a typo between MSG_REQUEUE and MSG_REJECT_REQUEUE.

Fix should be easy but not sure which of the two is preferred. I personally prefer the use of MSG_REJECT_REQUEUE.