Prototype a 3 isolate daemon

[adam-singer]

• isolate for reading the packages from pub.dartlang.org
• isolate for acting like a queue which the first isolate enqueues packages onto
• isolate for dequeue and launching/managing compute engine instances.

Testing an idea of using multiple isolates to manage the async and concurrency issues of having to read, check, queue, build, dequeue.

[adam-singer]

Prototype complete