* DEV: More robust processing of URLs
The previous `UrlHelper.encode_component(CGI.unescapeHTML(UrlHelper.unencode(uri))` method would naively process URLs, which could result in a badly formed response.
`Addressable::URI.normalized_encode(uri)` appears to deal with these edge-cases in a more robust way.
* DEV: onebox should use UrlHelper
* DEV: fix spec
* DEV: Escape output when rendering local links