check bundler version when deploying to make sure you're not deploying with old cap recipes

deploy.rb

# You could hard-code this, but we keep the current bundler version 
# everybody is supposed to use in a default.gems file. So you can 
#
#  rvm gemset empty
#  rvm gemset import
#  bundle install --local
#
# And you're in a known good state.
expected_bunder_version = File.read( File.join( File.dirname( __FILE__ ), '..', 'default.gems' ) ).match( 'bundler -v(\S+)' )[1]
if Bundler::VERSION != expected_bunder_version
  abort "Refusing to deploy with Bundler v#{Bundler::VERSION} (expecting v#{expected_bunder_version})"
end