Doctests are failing

[gdalle]

Tried to add doctests to runtests.jl in #190 and they exploded. My guess is the documentation outputs are slightly outdated

[pgrepds]

I have opened a PR. I have created a list of problematic doc tests, which I have deactivated, there as well.

[gdalle]

PR merged but the problematic doctests remain. Copying them

• modularity.jl has a reference on SimpleWeightedGraph which is not included by Graphs.jl.
• transitivity.jl in the function transitiveClosure. The issue here is that Documenter.jl truncates the output. Thus, it is not fully visible. We could compare the truncated output instead. However, it might then differ from the output which is seen by the user.
• shortestpaths.jl in the function has_negative_weight_cycle in src/Experimental. The SPFA package is not found. The same happens in spfa.jl.
• spfa.jl in spfa_shortest_paths. The output is compared to an error message. However, the full stack trace is obviously not included.
• euclidiagraphs.jl uses random values. We might want to add a local doc filter.
• randgraphs.jl uses random values. We might want to add a local doc filter here as well.