Bump version in cabal file for upload

ipython-kernel/ipython-kernel.cabal

 name:                ipython-kernel
-version:             0.8.4.0
+version:             0.9.0.0
 synopsis:            A library for creating kernels for IPython frontends
 
 description:         ipython-kernel is a library for communicating with frontends for the interactive IPython framework. It is used extensively in IHaskell, the interactive Haskell environment.