Zach has written a really cool article, but we get an exception trying to follow his steps. Unfortunately the server guy has removed the exception..and I'll try and comment on this post, but is this really the way to add custom js?
The custom movingstd() and showifgreater() Timelion functions can be found here. Shut down Kibana, add the functions to your Timelion source (kibana/installedPlugins/timelion/series_functions/<function_name>.js), delete the optimized bundle (rm kibana/optimize/bundles/timelion.bundle.js) and restart Kibana. The functions should be available for use in Timelion now.