More fixing of the Gentoo install instructions.

README.md

@@ -73,18 +73,22 @@ To install Haskell from the official repos on Arch Linux, run
 
 On Gentoo, you can install the individual components of the Haskell Platform
 through Portage. If you use `ACCEPT_KEYWORDS=arch` (as opposed to
-`ACCEPT_KEYWORDS=~arch`), `cabal-install` is likely to be masked, so you should
-probably run something like
+`ACCEPT_KEYWORDS=~arch`), Portage will install ancient versions of the various
+Haskell things. With that in mind, iff you use `ACCEPT_KEYWORDS=arch`, add the
+following to `/etc/portage/package.keywords`, replacing `amd64` with your
+architecture.
 
-    echo ">=dev-haskell/cabal-install-1.18.0.3 ~amd64" >> /etc/portage/package.keywords
+    >=dev-haskell/cabal-install-1.18.0.3 ~amd64
+    >=dev-lang/ghc-7.8.3 ~amd64
 
-Replacing `amd64` with your architecture. Once that is done,
+ Once that is done,
 
     emerge --jobs --ask --verbose dev-lang/ghc dev-haskell/cabal-install dev-haskell/happy dev-haskell/alex
 
 Gentoo keeps a "stable" (read: old) version of `cabal-install` in the Portage
 tree, so you'll want to use `cabal-install` to install the more recent version.
 
+    cabal update
     cabal install cabal-install
 
 ### Mac OS X