v1.0.0.rc.0

It's not a big deal, but using begin here and in some of the other functions seems a bit unnecessary.  For example, here the only thing outside of the begin is the info, message, so you could just write:

```ruby
def build_image(dir)
  ui.info("Building image based on Dockerfile in #{dir}")
  img = ::Docker::Image.build_from_dir(dir) do |output|
    log = JSON.parse(output)
    puts log['stream']
  end
rescue Excon::Errors::SocketError => e
  ui.fatal(connection_error)
  exit 1
end