For external links, don't prepend www.gov.uk

We were returning web_urls like this:
    https://www.gov.ukhttp://www.nhs.uk/ehic
Don't return an id for recommended-links

We are currently returning id's like this:
    https://www.gov.uk/apihttp://www.nhs.uk/ehic.json
Merge pull request #96 from alphagov/stop_mangling_recommended_links

Stop mangling recommended links