Add validation for scrapable fields
Addressed review comments
Merge pull request #52 from alphagov/scrapable_field_validation

Add validation for scrapable fields
Partial CSV export (scope's not right yet, no old_urls)
Remove ScrapeResult#field_value() in favour of ScrapeResult#field_values[]
Convert to markdown in the export
Scope exported values to site / completed groups
Export old_urls as part of CSV
Stop coupling the tests to seeds
Fix CSV error visiting site export
Add org abbreviation to ScrapeResult CSV
Rename old_urls to old_url, take out the hash element and go for a straight array
Add 'for_scraping' qualifier to UrlGroup#content_type
Resolve semantic tension between scrapable_url and scraped_url
Replace reference to field_value
Merge pull request #51 from alphagov/csv_export

Csv export
Merge commit '56d048399096fefe26931d92bb4b45d45f7df64f' into HEAD