Plots dependency

[fzierler]

We should think about whether we want this package to explicity return Plots.jl's plot-objects or to simply provide recipes that can be used by Plots.jl. If we go for the latter we only need RecipesBase.jl as a dependency - this would reduce load times significantly as the user only needs to load Plots.jl when they want to plot something. In addition this probably reduces the frequency of CompatHelper PRs due to Plots.jl.

[briederer]

I would also vote for providing Recipes.
Though I am not 100% sure if RecipesBase.jl is enough then, but we can try to just rely on this Package.

[fzierler]

I have a custom recipe in my not-yet public code that only relies on RecipesBase.jl that still has some issues but is usable. I will create a PR today so that we have a concrete example to discuss.

[fzierler]

I noticed that in my example there was a hidden Plots.jl-dependency. This might actually be addressed in a future version of RecipesBase.jl but the issue has been dormant for almost 4 years now JuliaPlots/RecipesBase.jl#15 . If load times at some point become an issue we could think about fixing this upstream but for now I think we can tolerate the load time.

Edit. See #14 for the specific example.

[briederer]

JuliaPlots/RecipesBase.jl#15 has been fixed. We should be able to get rid off Plots now.