Update README.md with PigeonHole sort

Author: Lucas Lemaire

README.md

@@ -93,6 +93,7 @@ Note: The projects where tested on Xamarin Studio (MonoDevelop) on OSX 10, and V
  * [Cycle Sort](Algorithms/Sorting/CycleSorter.cs).
  * [Gnome Sort](Algorithms/Sorting/GnomeSorter.cs).
  * [OddEven Sort](Algorithms/Sorting/OddEvenSorter.cs).
+ * [PigeonHole Sort](Algorithms/Sorting/PigeonHoleSorter.cs).
 
 #### Graphs:
  * Graph Search: