.travis.yml in hamlit-2.8.4 vs .travis.yml in hamlit-2.8.5

@@ -2,10 +2,10 @@
 cache: bundler
 branches:
   only:
     - master
 script:
-  - "bundle exec rake $TASK"
+  - "BACKTRACE=1 bundle exec rake $TASK"
 matrix:
   include:
     - rvm: 2.1.10
       env: TASK=test
     - rvm: 2.2.6