Refactored a few API accessors.
Merge pull request #435 from namusyaka/refactor-some-codes

Refactored a few API accessors.
Merge branch 'develop' of github.com:madkins/grape into develop

* 'develop' of github.com:madkins/grape: (148 commits)
  Stop testing Grape against unsupported Ruby 1.8.7 variants.
  Add missing quote in documentation
  Added a link to grape-active_model_serializers.
  Removed unused property.
  Update Exception Handling example, Closes #429
  Update CHANGELOG.md
  Removes param memoization in Grape::Request. Closes #428
  Bump version to 0.5.1.
  Preparing for release, 0.5.0.
  Update README.md
  Organize the release notes in fixes/features, ahead of 0.5.0.
  Fix #427: handle nested parameters with arrays correctly when using declared
  Formatting changes to README.md
  Changing README.md to place the `use Rack::CORS` code in the config.ru rather than in the Grape::API subclass
  Update CHANGELOG
  Handle correctly nested declared params
  Adding 'json' gem into the spec_helper
  Added the Twitter API example to explicitly unloadable constants.
  Better rewind semantics.
  Fix #417: Rails 4 does not rewind input, causes POSTed data to be empty.
  ...
Merge branch 'master' of github.com:intridea/grape into develop

* 'master' of github.com:intridea/grape:
  Refactored a few API accessors.