README.md in banditry-0.4.0 vs README.md in banditry-0.5.0

@@ -18,9 +18,12 @@
 
 Or install it yourself as:
 
     $ gem install banditry
 
+NB: Banditry likely works on earlier versions of Ruby, but is only tested
+against versions 2.3 and above.
+
 ## Usage
 
 ### Banditry::BanditMask
 
 Create a class which inherits from Banditry::BanditMask, and declare the