fix ipython directive, py3 and recent ipython changes
Made py3 fixes to conf.py.  Docs now compile on PY3 (good job @phaebz, @kermit666 and joris).
Also worked around recent breaking change to ipython https://github.com/ipython/ipython/pull/4504,
which somewhat deflates my theory that by having our own copy we can avoid having 
other packages changes break our build (they can, if they change the packages it depends on).
