Feature tests for post jumping, fix for #9 and fix for the render catalog ert test

I added a dependency on `dash.el` which provides such revolutionary and never heard of before features like list zipping. Make sure to run `carton install` before running tests again. You'll also of course need dash locally for development. I believe you can `package-install` it but personally I just use the version from https://github.com/magnars/dash.el