Child Structure + Plots

[MiGraber]

I think it would be better to organize the child so that the each plot has its own section:

\```{r}
plot1
\```
\```{r}
plot2
\```

This way it is easier to add title and generic text.

We should think about a proper object to handle this issue

[tuanle618]

added in PR #43 . I will try to clean up more.