Implement #flat_map for Promise
Implement #zip for Promise
Fix Promise#zip for Promise<Array>
Pass the executor to the child in Promise#flat_map
Use #wait instead of sleeping in Promise specs

The spec seems fragile otherwise
Handle failures in the block passed to Promise#flat_map
Use an ImmediateExecutor for Promise#flat_map not to schedule unneeded tasks
Merge pull request #158 from obrok/promise-composition

Promise composition
Create an IndirectImmediateExecutor
Implement IndirectImmediateExecutor with just one PerThreadExecutor
Add specs for IndirectImmediateExecutor characteristics
Merge pull request #165 from ruby-concurrency/actress

Remove actor-experimental warning.
Allow to disable auto termination of global executors

It was causing trouble when the gem was used in test-suites of other projects.
Merge pull request #167 from pitr-ch/pools

Allow to disable auto termination of global executors
Merge pull request #166 from obrok/indirect-immediate-executor

Create an IndirectImmediateExecutor
Add Promise.zip
Merge pull request #168 from obrok/promise-zip

Add Promise.zip
Better docs on Future.
Fix #173 leaking threads when pruning the pool
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