We use a gem package for solving door_3. We have tried to add multitple languages in build so we can run our gem package and pass our test.

.travis.yml

@@ -1,4 +1,13 @@
-language: python
+matrix:
+  include:
+    - language: ruby
+      rvm:
+        - 2.2
+        - jruby
+        - 2.0.0-p247
+      install: gem install zsteg
+
+    - language: python
       python:
         - 3.6
       install: