Add pool example

examples/pool.rb

@@ -0,0 +1,32 @@
+#!/usr/bin/env ruby
+
+$LOAD_PATH.push File.expand_path("../lib", __dir__)
+require 'celluloid/autostart'
+
+# This is required for pool to work as Celluloid doesn't load it by default
+require 'celluloid/pool'
+require 'prime'
+
+class PrimeWorker
+  include Celluloid
+
+  # Checks if a number is prime
+  def prime(number)
+    if Prime.prime?(number) 
+      puts number
+    end
+  end  
+end
+
+# Creates a pool of actors that is equal to the number of CPU cores present on
+# the machine
+pool = PrimeWorker.pool
+
+(2..1000).to_a.map do |i|
+  # Asynchronously calls prime method. Celluloid decides which actor to invoke
+  # out of the pool
+  pool.async.prime i 
+end
+
+# Keeps the main thread alive for long enough for our output to be displayed
+sleep 100