This is to bring the julia version information into accordance with
section 7.3.2 of the nixpkgs manual:
The version in the filename should leave out unnecessary detail.
For instance, if we keep the latest Firefox 2.0.x and 3.5.x
versions in Nixpkgs, they should be named firefox/2.0.nix and
firefox/3.5.nix, respectively (which, at a given point, might
contain versions 2.0.0.20 and 3.5.4).
Julia uses semantic versioning (http://semver.org), so the third
digit (the patch level) represents backwards-compatible bug fixes
only.
