Add the Phuedx\Czmq\Cert class

Currently, the Cert class provides a way to create certificates for the
ØMQ CURVE security mechanism.[0]

[0] http://rfc.zeromq.org/spec:26
Add the Phuedx\Czmq\Cert#apply method

Install the latest and greatest php-zmq as #apply accepts an instance of
the ZMQSocket class as an argument.