fix fiber edge case; brevity

revised fibers, removed implicit promise conversions

implicit promise interop

dramatically simpler, faster, more synchronous

`import 'posterus/fiber'` auto-chooses ES2015

actually publish ./es

ES modules for module concatenation support

* this makes Posterus compatible with Webpack's new module concatenation feature, leading to slightly cleaner and smaller bundles

Future.all no longer gets slower with large input arrays

* probably irrelevant in real world code, but could make us look bad in artificial microbenchmarks

bugfixed a rare edge case in .all and .race

unignore posterus/fiber for NPM, remove posterus/routine