Don't touch the default PHP-Redis connect timeout

When using Credis_Client without setting the 3rd argument (timeout) the BLPOP won't work correctly when the PHP-Extension is installed. However, it does work when you forceStandalone(). See this GIST for more details: https://gist.github.com/ruudk/49d5dd61222ae40094fc

That's why I've removed the default `$timeout = 2.5` from the constructor and moved it to the standalone `connect` method. 

Can this be merged?