My reluctance with going this route (javascript handlebars helpers vs `templateHelpers` in javascript) in the initial version of webview is that these libraries/helpers do not exist in python.

I think for mobile/low-bandwidth users will be unresponsive and we may need to render pages initially on the webserver.
It may not be an issue yet, but one of the reasons for choosing handlebars/mustache was that we still had an option to render on the server.

Aside: Would it be worth contributing these helpers to swag/assemble.io so we do not have to maintain them?