implementing issue 28. commit before test on dev1 server. (9)

28) add share icons to api_gift (one icon for each api provider)
    OK for facebook, google+, linkedin, Pinterest, twitter and vkontakte.
    todo:  add ajax spinner while fetching share url from server. Normally quick, but server is slow and small.
    todo:
    - Buffer: http://bufferapp.com/add?text={title}&url={url}
    - Digg: http://digg.com/submit?url={url}&title={title}
    - Tumblr: http://www.tumblr.com/share/link?url={url}&name={title}&description={desc}
    - Reddit: http://reddit.com/submit?url={url}&title={title}
    - StumbleUpon: http://www.stumbleupon.com/submit?url={url}&title={title}
    - Delicious: https://delicious.com/save?v=5&provider={provider}&noui&jump=close&url={url}&title={title}
    todo: change error handling in get_share_gift_link. Do not use alert. Use ajax error table under gift links
    todo: add ajax spinner when fetching deep link from server
    todo: gifts/show with deep link - reuse deep link in new share without refetching deep link from db
    todo: check http://developer.sharethis.com/Web_Share_API