Add LTS 14 to test matrix

Author: Porges

.travis.yml

@@ -23,6 +23,7 @@ env:
 - ARGS="--resolver lts-11"
 - ARGS="--resolver lts-12"
 - ARGS="--resolver lts-13"
+- ARGS="--resolver lts-14"
 - ARGS="--resolver lts"
 - ARGS="--resolver nightly"