Support For define.amd

Trying to use rollup for a refactor of Backburner with @krisselden and others. I noticed that rollup has AMD check looks for `define && define.amd`. Loader.js explicitly opts out of this with `define.petals`, wondering if people would be opposed to just setting `define.amd` to `true`. It's not spec compliant, however loader.js is already not spec compliant in this regard.