Centralise error handling, cope with offline case
Centralise error handling, cope with offline case

scraperwiki/code-scraper-in-browser-tool,scraperwiki/code-scraper-in-browser-tool,scraperwiki/code-scraper-in-browser-tool,scraperwiki/code-scraper-in-browser-tool,scraperwiki/code-scraper-in-browser-tool,scraperwiki/code-scraper-in-browser-tool,scraperwiki/code-scraper-in-browser-tool,scraperwiki/code-scraper-in-browser-tool,scraperwiki/code-scraper-in-browser-tool