It is absurd that for every programming language there must be a new package manager. rubygems, pip, CPAN, composer, npm, bower, etc. I highly recommend that folks look into what GNU Guix and Nix can do, because they are capable of being decentralized package management systems for any type of software. They both feature "profiles", which you could equate with bundles, gemsets, whatever they are called for your language. It's trivial to use multiple versions of the same package (let's say Ruby 1.9.3 and 2.0) for different projects without them conflicting. These software projects are relatively new, but keep your eye on them and give them a shot if you have a chance.

GNU Guix homepage: https://gnu.org/software/guix/

Nix homepage: http://nixos.org/