Add extra config for EA scraper

- Chart datum offset, so we can translate from Newlyn
- Site Datum, to compare against that reported by the website and blow
  up if it ever changes.

https://www.pivotaltracker.com/story/show/83203118 [#83203118]
Merge pull request #29 from sealevelresearch/extra-config-ea-scraper

Add extra config for EA scraper