exception handling for _config.yml

[geekodour]

the _config.yml files is fetch from the filesystem, but there's no exception handling in there, if there is error in _config.yml the error output is unhelpful.
used lines:
https://github.com/geekodour/gitpushblog/blob/master/scripts/init.js#L12
https://github.com/geekodour/gitpushblog/blob/master/scripts/nunjucks_config.js#L12