Add Event documentation example

Author: anildigital

lib/concurrent/atomic/event.rb

@@ -13,6 +13,27 @@ module Concurrent
   # `#reset` at any time once it has been set.
   #
   # @see http://msdn.microsoft.com/en-us/library/windows/desktop/ms682655.aspx
+  # @example
+  #   event = Concurrent::Event.new
+  #
+  #   t1 = Thread.new do
+  #     puts "t1 is waiting"
+  #     event.wait(1)
+  #     puts "event ocurred"
+  #   end
+  #
+  #   t2 = Thread.new do
+  #     puts "t2 calling set"
+  #     event.set
+  #   end
+  #
+  #   [t1, t2].each(&:join)
+  #
+  #   outputs
+  #   "t2 calling set"
+  #   "t1 is waiting"
+  #   "event ocurred"
+  #
   class Event < Synchronization::LockableObject
 
     # Creates a new `Event` in the unset state. Threads calling `#wait` on the