Rely on PECL for redis client

Hey jippi,

The redis client is now being packaged via PECL now. It doesn't seem like a custom package builder is needed. I've updated php::extension::redis to follow format of php::extension::igbinary.

Note: dotdeb has php5-redis as an available package now, but I prefer getting the latest from PECL as usually thats a bit more up-to-date vs custom package repos.