+ support for worker pause & resume initial commit
+ pause & resume will be extremely helpful in a few cases:
1. route traffic to some specific worker for debugging, warmup, testing purposes. (by pausing the rest)
2. performance tuning by pausing a worker, and do explicit gc, which allows us to use infrequent GC in normal its normal state
+ pause & resume implementation has an assumption that all app states have nothing to do with the server, it could be in the process mem space, tied to the express app, or elsewhere, but never tied to the actual tcp/http/https server. that's a prerequisite for efficient resume.
Merge pull request #7 from cubejs/cluster3

Cluster3 rebase
Merge pull request #52 from inexplicable/cluster3

pause & resume