Now all helpers can be overridden by custom implementations without editing JB source. Just define a helper's 'engine' as 'custom' in the _config.yml file and provide a helper file of the same name in _includes/custom/. This helps users cleanly upgrade JB versions since they no longer need to edit the files directly.
This makes GitHub Pages for projects support possible as all urls will need to call on the project's subfolder. The other important piece is that urls should resolve to root locally but be able to change when in production. LLastly this gives themes clear integration points for working with paths. (the jbcache hack just makes it so there is not unnecessary whitespace output in the source.