fixes for extracting content from fastcompany pages

Love this gem. This PR includes fixes for extracting content from articles on fastcompany.

* included [this article](http://www.fastcompany.com/most-innovative-companies/2012/airbnb) in the corpus and updated `metadata_expected.yaml` in kind
* add `.node-byline` to `AUTHOR_MATCHES`
* reject empty string titles (not just nil titles)
* update a couple `LEDE_MATCHES` selectors to avoid fastcompany's `p.advertisement` elements
* tidying: append `pwd` to `$LOAD_PATH` so `rake console` works