Cooler README build status line

Status line is now:
• Very first thing, above the header.
• Trailed by a double-space-seperated, `<small>`, parenthesized branch name, e.g.: `(master branch)`.
• `<img>` properly vertically aligned with the text.
• All HTML, because of `<img align=…` and `<small>`, and to make it not look afool.
Merge branch 'master' into feature/puck-dynamics

Also replace “master” with “feature/puck-dynamics” in the build status line (first line) of the README.md.