Adding multi-threading capabilities
implementing multi threading, pushing processes into background (#72)
* implementing multi threading, pushing processes into background
* added test for process runner, changed visibility of methods for testing
* reverted to older phpunit implementation
* Fix travis for PHP7 and dist trusty for HHHVM. (#74)
* Fix travis for PHP7 and dist trusty for HHHVM.
* Cache composer.
* Fix error "Only variables should be passed by reference"
* Fix PHPUnit reports
* Add codecov.
* implementing multi threading, pushing processes into background
* added test for process runner, changed visibility of methods for testing
* reverted to older phpunit implementation
* fixed issue with losing pid when process is finished but not cleaned up
* making sure the process is actually running and has pid before trying to send signal
* catching logical process exception