add grumble about using cabal update

README.md

@@ -5,6 +5,9 @@ IHaskell
 IHaskell is an implementation of the [IPython](http://ipython.org) kernel protocol which allows you to use Haskell inside IPython frontends such as `qtconsole` and `notebook`.
 
 [Demo Notebook](http://gibiansky.github.io/IHaskell/demo.html)
+
+**_Please_ run `cabal update` before installing - IHaskell updates _very_ regularly!**
+
 ---
 
 The project works with the IPython shell:
@@ -92,6 +95,7 @@ IHaskell Installation
 
 Install the IHaskell package from Hackage:
 ```bash
+cabal update # Please do this! IHaskell updates *very* frequently.
 cabal install ihaskell
 ```