"Share on twitter" button is now a link that opens in a new page.

This normally makes no difference because the twitter widget js opens a new popup when the button is clicked, regardless of the target attribute. However if the user is blocking the twitter widget library (e.g. he uses the Ghostery firefox plugin) the link becomes a regular link to a twitter page; in this case it's better that the link opens a new tab.
Pass an option hash so that the tooltip for entry buttons is attached to the page body.

This removes a bug in some browsers (at least Chrome) in which the buttons moved a bit to the left on mouseover.

See discussions about this issue:

https://github.com/twbs/bootstrap/issues/6811
https://github.com/twbs/bootstrap/pull/6378

The bootstrap docs, by the way, describe the "container" option for the "tooltip" function, but they don't really explain what it does nor that it fixes this issue.