916 new charts on top

Closes #916.
After pulling out a considerable amount of hair with the old design, decided to re-architect things slightly, and now new charts are added on top.
Note that I can't quite test that new charts are added on top because [async tests are broken for clojurescript.test](https://github.com/cemerick/clojurescript.test/issues/70), but I did add some other chart tests.
can you merge these two `let` statements?