Updated Predis to work with 1.*, not 0.8

I'm not sure if you'll have any use for this or be interested in any of the changes, but these are changes I made to get SncRedisBundle working with Predis 1.0 -- take them or leave them. Tests look to be passing (with two failures that were present before the changes I've made.)
Instances of  `Predis\Command\Command` cannot be casted to string anymore, see nrk/predis#151 for an explanation. The old behavior, if needed, can be re-implemented _externally_ by this bundle with an utility method that fetches the command arguments using `Predis\Command\Command::getArguments()` and prepares the string used to feed the logger.