Update README.md

Changes build tool requirement to any.
Update README.md

- Changes language to indicate that any language/framework can be used.

- Removes test case requirement.
add gemfile for necessary gems
add classes for Box and Book and setup up initialize methods as well as
a spec file
add tests for book creation
add tests for box creation and adding books to a box
add tests and functionality for for packing books into boxes and exporting as json
example of exported valid json into json file
clean up driver code
update spec for SimplePacker
update spec for exporter
add extensions file answering questions from repo
split classes into own files and require them in main book packer
add .rspec and spec helper
break out class specs into its own file