Resume Recommendations Request/Response

This change is to add resume recommendations to the external api wrapper.
In order to test, copy and paste the code below into terminal (replacing dev key with real one)..........

bundle
bundle exec pry
require 'Cb'

Cb.configure do |config|
  config.dev_key = 'place_dev_key_here'
  config.time_out = 30
  config.debug_api = true
end

client = Cb::Client.new
request = Cb::Requests::Recommendations::Resume.new({:resume_hash => '9b13d2082bfeb71d36d109ae300f066adaea64e6770ec055252f1c0dfb3eee09', :external_user_id => 'XRHN41N711FXMCP6CVQD'})

client.execute(request)
should we name this should have a nil body?