Update Travis CI job

.travis.yml

@@ -13,11 +13,11 @@ env:
  - GHCVER=7.8.1 CABALVER=1.18
  - GHCVER=7.8.2 CABALVER=1.18
  - GHCVER=7.8.3 CABALVER=1.18
- - GHCVER=head  CABALVER=1.20
+ - GHCVER=head  CABALVER=head
 
 matrix:
   allow_failures:
-   - env: GHCVER=head  CABALVER=1.20
+   - env: GHCVER=head  CABALVER=head
 
 before_install:
  - travis_retry sudo add-apt-repository -y ppa:hvr/ghc
@@ -32,7 +32,7 @@ install:
 script:
  - cabal configure -v2
  - cabal build -v2
- - cabal check
+ - if [ "$CABALVER" != "1.16" ]; then cabal check; fi
  - cabal sdist
 # The following scriptlet checks that the resulting source distribution can be built & installed
  - export SRC_TGZ=$(cabal info . | awk '{print $2 ".tar.gz";exit}') ;