Update README.md

Add donation link

Author: ChrisJStone

README.md

@@ -231,3 +231,12 @@ the command.
 The files should be placed in .git/hooks  
 In the directory hooks you can find examples of all the hooks available.
 
+
+## Showing your appreciation
+
+Of course, the best way to show your appreciation for the git-flow tool itself
+remains contributing to the community.  If you'd like to show your appreciation
+in another way, however, consider donating through PayPal:
+
+https://www.paypal.com/donate/?hosted_button_id=GU25NCHMVMT9U
+