Refactor `Raisin::Response`:

    - add new `format` method;
    - update `render` method: take data from `body` and format from `format`;
    - update `render_error` corresponding to the new `render` syntax;
Small fixes in the `Raisin.pm`:

    - clean up documentation;
    - remove useless comments;
    - set up format and data explicit to the `Raisin::Response`;
Update a POD's name
Remove DDP dependency
Update build tool
Reorganize tests
Update POD
Update documentation