Add capybara

For javascript heavy sites; having something that speaks javascript is a lot easier than mechanize. As a proof of concept, I got an odesker to rewrite the failing hobart scraper using capybara webkit - 
https://morph.io/CloCkWeRX/hobart-capybara-webkit

This site unfortunately used a lot of javascript to re-invent hyperlinks.
If this works, similar things can be done for Kingston, Adelaide, Port Adelaide-Enfield and many more ePathway based sites.


I really am not too sure how docker works; so this is completely untested(!), but I've added the relevant gems and dependencies.

The one remaining part is doing something like
```xvfb-run -a ruby scraper.rb``` - see https://github.com/thoughtbot/capybara-webkit#ci

... where it wasn't clear what the appropriate spot was.