Use SSHKit command_map

[hbin]

Same as seuros/capistrano-sidekiq#104

We don't need to explicitly specify the bundle exec statement(actually, we shouldn't).

The best practice is add the binaries to the bundle_bins array.

With following the best practice, the user can easily to custom the execution command, for example, I am going to use the dotenv executable to launch the puma. I can add an additive task like this:

namespace :bundler do
  task :map_bins do
    fetch(:bundle_bins).each do |command|
      SSHKit.config.command_map.prefix[command.to_sym].push('dotenv')
    end
  end
end