embed_original: change overflow for the iframe content from hidden to auto
Without this change only a portion of the original website is embedded
in Firefox 20. The Chromium 26 behavior is as expected with hidden and auto.
Merge pull request #141 from tptb/master

embed_original: change overflow for the iframe content from hidden to auto
implement support for multiple pub/mark buttons, add plugin which adds a separate mark button to article botton in combined mode (closes #382)