Allow passing options hash to a custom validator.
Calling  will now return the current content-type.
Filled out some specs for #716.
Enable RSpec rerun with Guard.
Fixed documentation for redirect

Default in doc was true but in code it was false.
Errors can now be presented with a Grape::Entity class.
Merge pull request #724 from GvS666/master

Fixed documentation for redirect
Small readme fix.

Method is called `requires` not `required`.
Merge pull request #728 from binarycleric/readme_fix

README references undefined method (requires not required)
Re-added Grape::API::Helpers for backward compatibility, broken in #716.
Preparing for release, 0.9.0.
Preparing for next development iteration, 0.9.1.
Typo
Merge pull request #741 from tomconroy/patch-1

Typo
Added `non_empty` parameter validator to validate non-empty strings