Different code snippets from the same doc string mixed up in playpen

[glacjay]

For example, http://doc.rust-lang.org/std/cell/index.html, when I click the top right arrow of the first code snippet, there are not only code from this snippet, but also the following snippets, one followed the other.

[killercup]

Just ran into this at the docs for HashMap.

Looks like this line of JavaScript selects to much code when building the code for the playpen link. I guess it should be prev instead of siblings. I'll look into writing a short PR.