Switch to built-in Travis Haskell support.

.travis.yml

-env:
- - GHCVER=7.0.1 CABALINSTALLVER=1.16
- - GHCVER=7.0.2 CABALINSTALLVER=1.16
- - GHCVER=7.0.3 CABALINSTALLVER=1.16
- - GHCVER=7.0.4 CABALINSTALLVER=1.16
- - GHCVER=7.2.1 CABALINSTALLVER=1.18
- - GHCVER=7.2.2 CABALINSTALLVER=1.18
- - GHCVER=7.4.1 CABALINSTALLVER=1.18
- - GHCVER=7.4.2 CABALINSTALLVER=1.18
- - GHCVER=7.6.1 CABALINSTALLVER=1.18
- - GHCVER=7.6.2 CABALINSTALLVER=1.18
- - GHCVER=7.6.3 CABALINSTALLVER=1.18
+language: haskell
 
-before_install:
- - sudo add-apt-repository -y ppa:hvr/ghc
- - sudo apt-get update
- - sudo apt-get install cabal-install-$CABALINSTALLVER ghc-$GHCVER
- - export PATH=/opt/ghc/$GHCVER/bin:$PATH
-
-install:
- - cabal-$CABALINSTALLVER update
- - cabal-$CABALINSTALLVER install --only-dependencies
- - ghc --version
+ghc:
+  - 7.0
+  - 7.2
+  - 7.4
+  - 7.6
+  - 7.8
 
 script:
- - cabal-$CABALINSTALLVER configure -v2
- - cabal-$CABALINSTALLVER build -v2
- - cabal-$CABALINSTALLVER check
- - cabal-$CABALINSTALLVER sdist
+ - cabal configure -v2
+ - cabal build -v2
+ - cabal check
+ - cabal sdist
 # The following scriptlet checks that the resulting source distribution can be built & installed
- - export SRC_TGZ=$(cabal-$CABALINSTALLVER info . | awk '{print $2 ".tar.gz";exit}') ;
+ - export SRC_TGZ=$(cabal info . | awk '{print $2 ".tar.gz";exit}') ;
    cd dist/;
    if [ -f "$SRC_TGZ" ]; then
-      cabal-$CABALINSTALLVER install "$SRC_TGZ";
+      cabal install "$SRC_TGZ";
    else
       echo "expected '$SRC_TGZ' not found";
       exit 1;