Detach themes from core JB framework.
When installing from a theme package we create an array of all files to be mirrored. We need to omit directories from this array since directories are recursively created for a given file. This needlessly raised 'directory already exist' errors which was annoying. - Also make error output friendlier
…e will still explicitly require a per-page tagline. Adding rvmrc to gitignore for those of us still using Ruby Version Manager.
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.