Error checking on setting the min_password_score

Warn on low values and raises an error if out of bounds.

lib/devise_zxcvbn.rb

@@ -3,8 +3,25 @@
 require "zxcvbn"
 
 module Devise
-  mattr_accessor :min_password_score
+
   @@min_password_score = 4
+
+  def self.min_password_score
+    @@min_password_score
+  end
+
+  def self.min_password_score=(score)
+    if score.is_a?(Integer) && (score >= 0 && score <=4)
+      if score >= 3
+        @@min_password_score = score
+      else
+        ::Rails.logger.warn "[devise_zxcvbn] A score of less than 3 is not recommended." 
+        @@min_password_score = score
+      end
+    else
+      raise "The min_password_score must be an integer and between 0..4"
+    end
+  end
 end
 
 Devise.add_module :zxcvbnable, :model => "devise_zxcvbn/model"