Ensure we get parallel dependency builds.

Author: Patrick Thomson

.travis.yml

@@ -29,10 +29,10 @@ before_install:
 
 install:
 - cabal new-update
-- cabal new-configure --enable-tests --write-ghc-environment-files=always
-- cabal new-build --only-dependencies
+- cabal new-configure --enable-benchmarks --enable-tests --write-ghc-environment-files=always
+- cabal new-build --only-dependencies -j
 
 script:
-- cabal new-build
+- cabal new-build -j
 - cabal new-test semantic:test
 - cabal check