update travis yml

there is some problem with node on travis server.
node doesn't required to build docker image anyway.

Author: wizzup

.travis.yml

@@ -1,11 +1,13 @@
 sudo: required
 
-language: node_js
-node_js:
-  - "5.8"
+language: javascript
 
 services:
   - docker
 
+after_success:
+  - docker ps -a
+  - docker images -a
+
 script:
-  - make recent
+  - make recent