update travis

Author: ocramz

.travis.yml

@@ -13,9 +13,10 @@ addons:
 # The different configurations we want to test. You could also do things like
 # change flags or use --stack-yaml to point to a different file.
 env:
-- ARGS="--resolver lts"  
+- ARGS="--resolver lts"
+- ARGS="--resolver nightly"
 ## - ARGS="--resolver lts-11.5"
-## - ARGS="--resolver lts-12.14"
+- ARGS="--resolver lts-12.14"
 - ARGS="--resolver nightly-2019-08-04"