Create an object in the first iteration, then add to it

[rafael.guerra]

@GlenHenshaw

> using Plots
> using UnicodePlots
> unicodeplots()
> plt1 = lineplot(Plots.fakedata(10), Plots.fakedata(10));
> plt2 = lineplot(Plots.fakedata(10), Plots.fakedata(10));
> plot([plt1 plt2])

ERROR: Cannot convert Matrix{Plot{BrailleCanvas}} to series data for plotting
Stacktrace:

using Plots; unicodeplots()
plt1 = plot(Plots.fakedata(5), Plots.fakedata(5));
plt2 = plot(Plots.fakedata(5), Plots.fakedata(5));
plot(plt1, plt2)

or: plot([plt1, plt2]...)