Add Jupyter cleanup

[miguelraz]

It would probably not be too hard for FemtoCleaner to update Jupyter notebooks.
I think educators would love the autoupgrading of their lectures.

If someone can outline a basic guideline of how to do this, I can take it on.

[fredrikekre]

import JSON, Deprecations

function update_notebook(infile, outfile = infile)
    nb = open(JSON.parse, infile)
    for cell in nb["cells"]
        if cell["cell_type"] == "code"
            old_source = join(cell["source"])
            _, new_source = Deprecations.edit_text(old_source)
            new_source = split(new_source, '\n')
            @views map!(x -> x * "\n", new_source[1:end-1], new_source[1:end-1])
            cell["source"] = new_source
        end
    end
    open(io -> JSON.print(io, nb, 1), outfile, "w")
end

[KristofferC]

Need a while loop over edit_text so that it will run until convergence, see:

FemtoCleaner.jl/src/FemtoCleaner.jl

Lines 80 to 89 in f3f6a1f

	while Deprecations.edit_file(fpath, deps, endswith(fpath, ".jl") ? edit_text : edit_markdown;
	analysis = file_analysis)
	if iteration_counter > max_iterations
	warn("Iterations did not converge for file $file")
	problematic_file = true
	break
	end
	iteration_counter += 1
	changed_any = true
	end

[miguelraz]

... this is the sort of Swedish efficiency that scares me for the world cup.
I'll try to whip this into a PR by day's end.
Thank you both for the intimidating input!