Major improvments

/cc @ciniglio @sshillo 

- Refactored method names
  - `where_params_eq` is now `with_params`
  - `route_params` is now `grape_documentation`
- Support for group, order, join
- Added support for grape-0.5.0
- Removed support for grape-0.4.x
- Coveralls works, I think?
- Corrected docs