DAG in tutorial does not work on Julia v1.1

[matsueushi]

GraphViz.jl is used in the tutorial, but it seems to be unmainted and does not support Julia v1.x.

epatters/Catlab.jl#24 (comment)

   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.1.0 (2019-01-21)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> import Pkg; Pkg.add("GraphViz")
  Updating registry at `~/.julia/registries/General`
  Updating git-repo `https://github.com/JuliaRegistries/General.git`
 Resolving package versions...
ERROR: Unsatisfiable requirements detected for package GraphViz [16d363e1]:
 GraphViz [16d363e1] log:
 ├─possible versions are: [0.0.1-0.0.4, 0.1.0-0.1.1] or uninstalled
 ├─restricted to versions * by an explicit requirement, leaving only versions [0.0.1-0.0.4, 0.1.0-0.1.1]
 └─restricted by julia compatibility requirements to versions: uninstalled — no versions left
Stacktrace:
 [1] #propagate_constraints!#61(::Bool, ::Function, ::Pkg.GraphType.Graph, ::Set{Int64}) at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.1/Pkg/src/GraphType.jl:1005
 [2] propagate_constraints! at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.1/Pkg/src/GraphType.jl:946 [inlined]
 [3] #simplify_graph!#121(::Bool, ::Function, ::Pkg.GraphType.Graph, ::Set{Int64}) at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.1/Pkg/src/GraphType.jl:1460
 [4] simplify_graph! at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.1/Pkg/src/GraphType.jl:1460 [inlined] (repeats 2 times)
 [5] resolve_versions!(::Pkg.Types.Context, ::Array{Pkg.Types.PackageSpec,1}, ::Nothing) at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.1/Pkg/src/Operations.jl:371
 [6] resolve_versions! at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.1/Pkg/src/Operations.jl:315 [inlined]
 [7] #add_or_develop#63(::Array{Base.UUID,1}, ::Symbol, ::Function, ::Pkg.Types.Context, ::Array{Pkg.Types.PackageSpec,1}) at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.1/Pkg/src/Operations.jl:1171
 [8] #add_or_develop at ./none:0 [inlined]
 [9] #add_or_develop#15(::Symbol, ::Bool, ::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::Function, ::Pkg.Types.Context, ::Array{Pkg.Types.PackageSpec,1}) at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.1/Pkg/src/API.jl:54
 [10] #add_or_develop at ./none:0 [inlined]
 [11] #add_or_develop#14 at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.1/Pkg/src/API.jl:31 [inlined]
 [12] #add_or_develop at ./none:0 [inlined]
 [13] #add_or_develop#13 at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.1/Pkg/src/API.jl:29 [inlined]
 [14] #add_or_develop at ./none:0 [inlined]
 [15] #add_or_develop#12(::Base.Iterators.Pairs{Symbol,Symbol,Tuple{Symbol},NamedTuple{(:mode,),Tuple{Symbol}}}, ::Function, ::String) at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.1/Pkg/src/API.jl:28
 [16] #add_or_develop at ./none:0 [inlined]
 [17] #add#20 at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.1/Pkg/src/API.jl:59 [inlined]
 [18] add(::String) at /Users/osx/buildbot/slave/package_osx64/build/usr/share/julia/stdlib/v1.1/Pkg/src/API.jl:59
 [19] top-level scope at none:0

ForneyLab.jl provides dot2svg for Julia v1.x.

import ForneyLab.dot2svg

>>> display("image/svg+xml", dot2svg(graph2dot(model)))