travis: run js/test py/test targets

We can use nodejs and python in travis without installation (though we
don't know their version).

https://docs.travis-ci.com/user/ci-environment/#Runtimes

Author: haya14busa

.travis.yml

@@ -16,7 +16,7 @@ matrix:
       - MAKE_TARGET=test
     - env:
       - VIM_VERSION=installed
-      - MAKE_TARGET="clean_compiled check"
+      - MAKE_TARGET="clean_compiled check js/test py/test"
 
 install:
   - |