Now developers can pass a client object or an executable context (see
Predis\Transaction\MultiExecContext or Predis\Pipeline\PipelineContext)
interchangeably as parameters to their methods using the new interface
Predis\BasicCliantInterface.
These new interfaces will also allow us to easily create new client
classes aside from the standard Predis\Client one.
Starting with 2.6, Redis uses a slightly different format for the payload
returned by MONITOR for each command. Predis can now adapt to this difference
and returns a new `client` field in the payload object. This new field is
always defined but is set to NULL when connected to Redis < 2.6.
Please note that Redis 2.6 now does not echo the `MONITOR` command as the
first payload when opening a new MONITOR context.
Alexandru Patranescu
Daniele Alessandri