updated sailthru client to accepts opts hash on construction as well as set default values for timeouts
set @opts instance var to what was given to the ctor instead of an empty hash
added SailthruUnavailableException class; use SailthruUnvailableException class for all timeout errors
added various other exception types to be caught and re-raised as a SailthruUnavailableException
use catch-all block for exceptions other than timeouts
also catch ETIMEDOUT errors