Add travis builds.

Author: cdepillabout

.travis.yml

@@ -37,30 +37,38 @@ matrix:
     compiler: ": #GHC 8.2.2"
     addons: {apt: {packages: [cabal-install-2.0,ghc-8.2.2,happy-1.19.5,alex-3.1.7], sources: [hvr-ghc]}}
 
+  - env: BUILD=cabal GHCVER=8.4.1 CABALVER=2.0 HAPPYVER=1.19.5 ALEXVER=3.1.7
+    compiler: ": #GHC 8.4.1"
+    addons: {apt: {packages: [cabal-install-2.0,ghc-8.4.1,happy-1.19.5,alex-3.1.7], sources: [hvr-ghc]}}
+
   # Build with the newest GHC and cabal-install. This is an accepted failure,
   # see below.
   - env: BUILD=cabal GHCVER=head  CABALVER=head HAPPYVER=1.19.5 ALEXVER=3.1.7
     compiler: ": #GHC HEAD"
     addons: {apt: {packages: [cabal-install-head,ghc-head,happy-1.19.5,alex-3.1.7], sources: [hvr-ghc]}}
 
+  # The Stack LTS builds.
+
   # Build using the configuration specified in the stack.yaml file in the
   # current directory.
   - env: BUILD=stack ARGS=""
     compiler: ": #stack default"
     addons: {apt: {packages: [libgmp-dev]}}
 
-  # The Stack LTS builds.
-  # (There are currently none because as of 2018-02-27,
-  # servant-checked-exceptions depends on servant >= 0.12, but the latest lts
-  # release only uses servant-0.11).
+  - env: BUILD=stack ARGS="--resolver lts-11"
+    compiler: ": #stack 8.2.2"
+    addons: {apt: {packages: [libgmp-dev]}}
+
 
   # Nightly builds are allowed to fail
   - env: BUILD=stack ARGS="--resolver nightly"
     compiler: ": #stack nightly"
     addons: {apt: {packages: [libgmp-dev]}}
 
   # Build on OS X with Stack in addition to Linux.
-  # (There are currently no builds for the same reason as above.)
+  - env: BUILD=stack ARGS="--resolver lts-11"
+    compiler: ": #stack 8.2.2 osx"
+    os: osx
 
   - env: BUILD=stack ARGS="--resolver nightly"
     compiler: ": #stack nightly osx"