convert and thumb format goes in as an option (making it easier to add support for e.g. frames later)
generators update the url_attributes name
deprecation messages for Dragonfly[:name], bad configuration and old datastores
rename Dragonfly.log -> Dragonfly.logger
added Dragonfly.debug (and tests for other logger methods)
fixed shell_commands_spec - no idea why it was passing
removed suppressing_stderr in tests
Shell uses Open3.popen3, not backticks, meaning we can control stderr