readme updates for 0.2.3
readme updates for 0.2.3

jcb91/IPython-notebook-extensions,juhasch/IPython-notebook-extensions,juhasch/IPython-notebook-extensions,ipython-contrib/IPython-notebook-extensions,ipython-contrib/IPython-notebook-extensions,juhasch/IPython-notebook-extensions,ipython-contrib/IPython-notebook-extensions,jcb91/IPython-notebook-extensions,ipython-contrib/IPython-notebook-extensions,jcb91/IPython-notebook-extensions