The internal ABI for ipython has changed between ipython version 2 and
3. In its current state, the result processor only works with IPython
version 2, so fail if the user wants to use the result processor with
the wrong version.
Abstract the ipython interface to a file so that we can make it support
versions 2 and 3 at the same time.
This result processor displays a desktop notification when the run
finishes. It's useful when you are running a long agenda in WA and want
to be notified when the results are available.
