* Renamed SingleConnectionInterface to NodeConnectionInterface since
this name is better and makes even more sense in the context of
cluster and replication scenarios.
* Moved specialized aggregate connections (the ones implementing both
predis and redis cluster and master/slave replication) in a newly
created Predis\Connection\Aggregate sub-namespace.
* Removed the "Connection" part from names of aggregate connection
interfaces in the Predis\Connection\Aggregate sub-namespace.
* Changed "Composable" to "Composite" in the name of interfaces and
classes that can use pluggable protocol processors.
We now have a base test case class for Predis (namely PredisTestCase)
grouping various commonly used utility methods shared by all of the
tests in the suite, greatly improving reusability.
First of all we completely removed the concept of pipeline executors.
Now pipelines can be easily customized by extending our default class
Predis\Pipeline\Pipeline.
Tests coverage for the Predis\Pipeline namespace is decent but can be
definitely improved while test cases can be beautified.