Pin rexml to 3.3.0

Author: samuelpx

gem_config.rb

@@ -48,6 +48,7 @@ def self.testing_and_debugging_dependencies
      ["webmock", "~> 3.18", ">= 3.18.1"],
      ["simplecov", "~> 0.22.0"],
      ["simplecov-cobertura", "~> 2.1.0"],
-     ["webrick", "~> 1.8", ">= 1.8.1"]]
+     ["webrick", "~> 1.8", ">= 1.8.1"],
+     ["rexml", "3.3.0"]]
   end
 end