Try catting the mkmf.log file if there is a failure

Author: tenderlove

.travis.yml

@@ -9,6 +9,9 @@ addons:
     packages:
       - libgmp-dev
 
+after_failure:
+  - "find . -name mkmf.log -exec cat {} \\;"
+
 env:
   - USE_MINI_PORTILE=true
   - USE_MINI_PORTILE=false