Attempt to bring up CI.

.travis.yml

@@ -0,0 +1,38 @@
+language: c
+
+cache:
+  directories:
+    - $HOME/.cabal/packages
+    - $HOME/.cabal/store
+
+before_cache:
+  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/build-reports.log
+  # remove files that are regenerated by 'cabal update'
+  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/00-index.*
+  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/*.json
+  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/01-index.cache
+  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/01-index.tar
+  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/01-index.tar.idx
+
+  - rm -rfv $HOME/.cabal/packages/head.hackage
+
+matrix:
+  include:
+    - compiler: "ghc-8.6.4"
+      addons: {apt: {packages: [cabal-install-2.4,ghc-8.6.4], sources: [hvr-ghc]}}
+
+before_install:
+- mkdir -p $HOME/.local/bin
+- "PATH=/opt/ghc/bin:$HOME/local/bin:$PATH"
+- ghc --version
+- cabal --version
+
+install:
+- cabal new-update
+- cabal new-configure --enable-benchmarks --enable-tests --write-ghc-environment-files=always
+- cabal new-build --only-dependencies
+
+script:
+- cabal new-build
+- cabal new-test semantic:test
+- cabal check