Fix hoe issue in Gemfile

Author: MSP-Greg

Gemfile

@@ -12,6 +12,9 @@ gem "mini_portile", "~>0.6.2", :group => [:development, :test]
 gem "hoe-bundler", "~>1.0", :group => [:development, :test]
 gem "hoe-gemspec", "~>1.0", :group => [:development, :test]
 gem "rdoc", ">=4.0", "<6", :group => [:development, :test]
-gem "hoe", "~>3.17", :group => [:development, :test]
+
+# hoe versions >= 3.19.0 are incompatible with Ruby 2.0 and earlier,
+# but the gemspec does not indicate so...
+gem "hoe", (RUBY_VERSION < "2.1" ? "3.18.1" : "~>3.20"), :group => [:development, :test]
 
 # vim: syntax=ruby