Removed shell.py entirely and made the embedded shell a proper subclass....
Removed shell.py entirely and made the embedded shell a proper subclass.
This created a new model :mod:`IPython.core.embed` with a subclass
of :class:`IPython.core.iplib.InteractiveShell` called
:class:`InteractiveShellEmbed`. This subclass now has all the embedding
logic that was in :mod:`shell`.
