Update ruby-puma to 2.16.0.

=== 2.16.0 / 2016-01-27

* 7 minor features:

  * Add 'set_remote_address' config option
  * Allow to run puma in silent mode
  * Expose cli options in DSL
  * Support passing JRuby keystore info in ssl_bind DSL
  * Allow umask for unix:/// style control urls
  * Expose `old_worker_count` in stats url
  * Support TLS client auth (verify_mode) in jruby

* 7 bug fixes:

  * Don't persist before_fork hook in state file
  * Reload bundler before pulling in rack. Fixes #859
  * Remove NEWRELIC_DISPATCHER env variable
  * Cleanup C code
  * Use Timeout.timeout instead of Object.timeout
  * Make phased restarts faster
  * Ignore the case of certain headers, because HTTP

* 1 doc changes:

  * Test against the latest Ruby 2.1, 2.2, 2.3, head and JRuby 9.0.4.0 on Travis

* 12 merged PRs
  * Merge pull request #822 from kwugirl/remove_NEWRELIC_DISPATCHER
  * Merge pull request #833 from joemiller/jruby-client-tls-auth
  * Merge pull request #837 from YuriSolovyov/ssl-keystore-jruby
  * Merge pull request #839 from mezuka/master
  * Merge pull request #845 from deepj/timeout-deprecation
  * Merge pull request #846 from sriedel/strip_before_fork
  * Merge pull request #850 from deepj/travis
  * Merge pull request #853 from Jeffrey6052/patch-1
  * Merge pull request #857 from zendesk/faster_phased_restarts
  * Merge pull request #858 from mlarraz/fix_some_warnings
  * Merge pull request #860 from zendesk/expose_old_worker_count
  * Merge pull request #861 from zendesk/allow_control_url_umask

(taca)