we don't need a separate handler for in-place form submission.
add by_url scope for searching links by normalized, heuristically-parsed url.
make url and source_locale read-only and add validations to ensure that title and summary are not set in first step of link creation.
we don't need these requires since we're using spork -- and add pry as irb-replacement.
update features so they pass.
if a link already exists with a given url, return that link instead of creating a new one.
clean up link default values spec section.