JSON constant name clashing fix

this prevents the following exception:
undefined method `pretty_generate' for ReqresRspec::Formatters::JSON:Class
 (NoMethodError)
Merge pull request #16 from sumskyi/exception-fix

JSON constant name clashing fix
bump version
Update LICENSE.txt
detect mime types when upload to S3
Merge pull request #18 from reqres-api/detect_mime_type_for_s3_files

detect mime types when upload to S3
bump version