Add --stacktrace option to Travis CI run
Add --stacktrace option to Travis CI run

.. for easier diagnosis

anuraaga/armeria,line/armeria,dongjinleekr/armeria,kojilin/armeria,imasahiro/armeria,line/armeria,kojilin/armeria,kojilin/armeria,dongjinleekr/armeria,line/armeria,jmostella/armeria,dongjinleekr/armeria,minwoox/armeria,minwoox/armeria,kojilin/armeria,anuraaga/armeria,trustin/armeria,dongjinleekr/armeria,jmostella/armeria,trustin/armeria,anuraaga/armeria,imasahiro/armeria,trustin/armeria,imasahiro/armeria,anuraaga/armeria,minwoox/armeria,jonefeewang/armeria,minwoox/armeria,anuraaga/armeria,dongjinleekr/armeria,trustin/armeria,jmostella/armeria,trustin/armeria,jonefeewang/armeria,line/armeria,kojilin/armeria,imasahiro/armeria,line/armeria,jonefeewang/armeria,anuraaga/armeria,jonefeewang/armeria,line/armeria,jonefeewang/armeria,jmostella/armeria,kojilin/armeria,jmostella/armeria,minwoox/armeria,minwoox/armeria,imasahiro/armeria,trustin/armeria