The only change from the version published at https://dev.twitter.com/docs/follow-button is that new lines have been removed.
Note that the src URL is given without a protocol (ie "http" or "https"). It's done this way so that it works on sites whether they are hosted on a HTTP or HTTPS domain. If you want the Twitter button to work while using a TiddlyWiki offline on a "file://" URL, then you'll need to manually add the protocol. For example: