serialize by Zend\Serialize (issue #33)

This version introduces multiple enhancements:

added required zend packages
apply composer to load example files

Details of additions/deletions below:
--------------------------------------------------------------

Modified:   composer.json
            -- Added --
                zendframework/zend-serializer 2.*
                zendframework/zend-servicemanager 2.*

Modified:   .gitignore
            -- Added --
                ignore vendor directory

Modified:   examples/base_object.php
            -- Updated --
                all require replaced by composer autoloader

Modified:   examples/register.php
            -- Updated --
                all require replaced by composer autoloader

Modified:   examples/xml.php
            -- Updated --
                all require replaced by composer autoloader