bang.el has been renamed to dash.el
Get it here: https://github.com/magnars/dash.el
Renaming a project is such a hassle. There has to be some good reason.
In ruby, methods often have two forms - with or without the !. The
method with a bang is then destructive. The functions in dash on the
other hand are all non-destructive, pure functions.
Looking at code with bangs everywhere was noisy. So while bang was a fitting name in that regard, the dash looks a lot better.
Ahem, sorry. But while bang brings up images of explosions and brute
force, dash is speedy and elegant. Not too shabby of a name I'd say.