get() method signature less optimal than it could be

It'd be great to move the $cas_token parameter to the second place as $cas_token is more likely to be used with get() than $callback. At least it would seem that way given the existence of two callback-focused/requiring functions: getDelayed and getDelayedByKey.

Due to this already being in use, it may need some type detection so that the two parameters technically become interchangeable within the signature, but we throw a deprecation warning (starting with 1.1) that states that $cas_token should come second going forward.

Additionally in 1.0.3, the callback for get() does not seem to be called--erroneous variable name output doesn't throw any errors, and basic echo's don't ever "surface" into the buffer.

Thanks.