remove Zend namespace

I suggest removing Zend namespace for simpler integration ;)

Also according to ZF guidelines (http://framework.zend.com/manual/en/coding-standard.naming-conventions.html)

"Note: Important: Code that must be deployed alongside Zend Framework libraries but is not part of the standard or extras libraries (e.g. application code or libraries that are not distributed by Zend) must never start with "Zend_" or "ZendX_". "