Updates for CI.

Author: ondrap

.travis.yml

@@ -8,8 +8,10 @@ matrix:
       addons: {apt: {packages: [cabal-install-1.22,ghc-7.10.1],sources: [hvr-ghc]}}
     - env: CABALVER=1.24 GHCVER=8.0.1
       addons: {apt: {packages: [cabal-install-1.24,ghc-8.0.1], sources: [hvr-ghc]}}
+    - env: CABALVER=head GHCVER=head
+      addons: {apt: {packages: [cabal-install-head,ghc-head], sources: [hvr-ghc]}}
   allow_failures:
-    - env: CABALVER=1.24 GHCVER=8.0.1
+    - env: CABALVER=head GHCVER=head
 
 before_install:
   - export PATH=/opt/ghc/$GHCVER/bin:/opt/cabal/$CABALVER/bin:$PATH