update gemfile
Validity period param is in seconds.

Make this clear in the ValidityPeriodConverter helper, and update the
README to reflect the correct units.
Update documentation to reference r509 org and http://r509.org
Move loading/printing of config out of config.ru and support reload via USR2

* Same as r509-ocsp-responder, move the loading/printing of the config out
  of config.ru and into a newly created R509::CertificateAuthority::HTTP::Config
  class.
* Trap the USR2 signal to reload the config

Fixes #11.
Merge pull request #29 from reedloden/split-config-out

Move loading/printing of config out of config.ru and support reload via USR2
Merge pull request #30 from reedloden/docs

Update documentation to reference r509 org and http://r509.org
Merge pull request #28 from jof/more_clear_validity_period

Validity period param is in seconds.