Keyword argument fix

Author: JonasJasas

examples/conversions_chaining.rb

@@ -14,7 +14,7 @@
 
 puts "Conversions done. Cost: #{jpg_result.conversion_cost}. Total files created: #{jpg_result.files.count}"
 
-zip_result = ConvertApi.convert('zip', Files: jpg_result.files)
+zip_result = ConvertApi.convert('zip', {Files: jpg_result.files})
 
 puts "Conversions done. Cost: #{zip_result.conversion_cost}. Total files created: #{zip_result.files.count}"