Add `cabal` to PATH in travis script

.travis.yml

@@ -8,26 +8,26 @@ before_install:
   - sudo add-apt-repository -y ppa:hvr/ghc
   - sudo apt-get update
   - sudo apt-get install cabal-install-1.18 ghc-$GHCVER
-  - export PATH=/opt/ghc/$GHCVER/bin:$PATH
+  - export PATH=/opt/ghc/$GHCVER/bin:/opt/cabal/1.18/bin:$PATH
 
 install:
-  - cabal-1.18 update
-  - cabal-1.18 install happy
+  - cabal update
+  - cabal install happy
   - export PATH=$HOME/.cabal/bin:$PATH
   - happy --version
-  - cabal-1.18 install --only-dependencies --enable-tests
+  - cabal install --only-dependencies --enable-tests
 
 script:
-  - cabal-1.18 configure --enable-tests
-  - cabal-1.18 build
-  - cabal-1.18 test
-  - cabal-1.18 check
-  - cabal-1.18 sdist
+  - cabal configure --enable-tests
+  - cabal build
+  - cabal test
+  - cabal check
+  - cabal sdist
   # The following scriptlet checks that the resulting source distribution can be built & installed
-  - export SRC_TGZ=$(cabal-1.18 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-1.18 install --enable-tests "$SRC_TGZ";
+      cabal install --enable-tests "$SRC_TGZ";
     else
       echo "expected '$SRC_TGZ' not found";
       exit 1;