Added 'CABALVER=1.24 GHCVER=8.0.1' combination to test matrix.

Author: svenpanne

.travis.yml

@@ -50,6 +50,14 @@ matrix:
          packages:
           - cabal-install-1.22
           - ghc-7.10.3
+   - env: CABALVER=1.24 GHCVER=8.0.1
+     addons:
+       apt:
+         sources:
+          - hvr-ghc
+         packages:
+          - cabal-install-1.24
+          - ghc-8.0.1
    - env: CABALVER=head GHCVER=head
      addons:
        apt: