More examples and tweaks

* Signal dispatch() method now uses own pid as default value
* SharedData now updates checksum cache on set()

src/Signal/Signal.php

@@ -17,8 +17,8 @@ class Signal
         pcntl_signal($this->signo, $handler);
     }
 
-    public function dispatch($pid):bool
+    public function dispatch($pid=null):bool
     {
-        return posix_kill($pid, $this->signo);
+        return posix_kill($pid?:posix_getpid(), $this->signo);
     }
 }