get_string_urls before putting urls into a set to avoid unhashable 'dict'
error when dealing with h-cite style in-reply-tos
Added new test cases for p-repost-of style repost-context (previously
caused unhashable dict error)
Merge pull request #7 from kylewm/h-cite-urls

get_string_urls before putting urls into a set to avoid unhashable 'dict'