[Process] Adding file existence check to pid_file loading
[System] Using a hash of fields instead of array indexes for ps_aux method to improve readability
[System] Taking into account the nil-argument case for #pid_alive?
[System] Adding check to #pid, and adding a method to delete a process' pid_file
[Process] Adding start and stop commands for a process
[Process] Adding utility proxies for alive? and dead? calls
[Process] Adding the process#stop method
[ProcessSpec] Adding nil stop_command case to process specs
[Process] Adding pid file removal to start command