Test with lts-2 again

Author: hce

.travis.yml

@@ -17,6 +17,7 @@ addons:
 # change flags or use --stack-yaml to point to a different file.
 env:
 - ARGS=""
+- ARGS="--resolver lts-2"
 - ARGS="--resolver lts-3"
 - ARGS="--resolver lts"
 - ARGS="--resolver nightly"