Update README.md

https://github.com/sailthru/sailthru-ruby-client/issues/33
bugzid 7799 update :optout and :hardbounce to strings
Merge pull request #34 from sailthru/bug-7799

bugzid 7799 update :optout and :hardbounce to strings
bump version and update changelog
bugzid:8397 - add removal of controller key in postback verification
Merge pull request #36 from sailthru/bug-8397

bugzid:8397 - add removal of controller key in postback verification
bugzid:7238 - Add Options to jobs
Merge pull request #37 from sailthru/bug-7238

bugzid:7238 - Add Options to jobs
Removing assignment of vars in deprecated #send method
Merge pull request #39 from knadeem/remove-assignment-in-send

Removing assignment of vars in deprecated #send method
Better handling of HTTP Timeouts

  - accept hash of options upon Sailthru client construction
  - set http_ssl_timeout, http_open_timeout, and http_empty_on_close using
    either values from the options hash or the default values in case these
    are not set
  - added a new exception type for Sailthru unavailability
    (SailthruUnavailableException)
  - catch Timeout::Error and Errno::ETIMEDOUT, re-raising them as a
    SailthruUnavailableException
Merge pull request #41 from AudioAddict/timeout-error-handling

Better handling of HTTP Timeouts
update gem from upstream