Adds support for using puma config file in capistrano deploys.

* Unless puma_config_file given ./config/puma/<env>.rb is used.
* Fallback to using puma_* variables if config file cannot be found.
Merge pull request #315 from jakubpawlowicz/master

Adds support for using puma config file in capistrano deploys.
Correct Typo in README.md

Fixed "Constaints" to read "Constraints"
Setup :worker_boot as an Array. Fixes #317
Merge pull request #316 from jcbantuelle/master

Fix Typo In Readme
Detect when the jruby daemon child doesn't start properly
Add ability to drain accept socket on shutdown
Add phased restart to capistrano recipe.

Add phased restart task.
Little refactor. Do not use fetch when no needed.