updated debian/ubuntu required packages

README

@@ -22,10 +22,10 @@ On Fedora, these can be installed with:
   yum install cabal-install ghc ghc-parsec-devel ghc-QuickCheck-devel ghc-json-devel ghc-regex-compat-devel
 
 On Ubuntu and similar, use:
-  ghc libghc-parsec3-dev libghc-json-dev libghc-regex-compat-dev libghc-quickcheck2-dev
+  apt-get install ghc libghc-parsec3-dev libghc-json-dev libghc-regex-compat-dev libghc-quickcheck2-dev cabal-install
 
 For older releases, you may have to use:
-  ghc6 libghc6-parsec3-dev libghc6-quickcheck2-dev libghc6-json-dev libghc-regex-compat-dev
+  apt-get install ghc6 libghc6-parsec3-dev libghc6-quickcheck2-dev libghc6-json-dev libghc-regex-compat-dev cabal-install
 
 Executables can be built with cabal. Tests currently still rely on a Makefile.