Good bye isolates, Node.js hardly knew ye

A feature on the Node.js 0.8.x roadmap was isolates, which would allow for threads-like features without the complexity of threads.  That's because isolates have no shared state, while allowing for multiple independent code execution streams to run in parallel within the same process.

This morning a check-in to the Node development tree backed out the support for isolates.  The explanation is pasted in below.

Revert support for isolates. It was decided that the performance benefits that isolates offer (faster spin-up times for worker processes, faster inter-worker communication, possibly a lower memory footprint) are not actual bottlenecks for most people and do not outweigh the potential stability issues and intrusive changes to the code base that first-class support for isolates requires. Hence, this commit backs out all isolates-related changes. Good bye, isolates. We hardly knew ye.