Introspection methods

This commit adds methods to get information about the state
of our phpredis object, such as what host/port we are connected
to, our timeout, etc...

The following methods have been added:

getHost()
getPort()
getDBNum()
getTimeout()
getReadTimeout()
isConnected()
getPersistentID()
getAuth()

In addition, there is a small memory leak fix when a persistent id
was specifically passed to connect() (it wasn't beeing freed).

Addresses issue #320
Merge branch 'hotfix/inspection_methods'