Renamed process item constant names
Removed ``$ipc->destroy()`` on contructor of Item
Added a tag to ignore coverage
Added a file checking before getting data
Updated return of wait() and stop() method

* Increased coverage of this methods;
* Now the return o stop() is the return of posix_kill();
* Now the return o wait() is the status of pcntl_waitpid().
Merge branch 'develop'