Allow error! to support objects

[aaronchi]

Most apis return some kind of error object when they return an error. It would be nice if grape supported any kind of input into the error! method and then parsed and returned it in the requested format

[mbleigh]

This is definitely something that will be on the roadmap. Because errors break the normal flow of things, they currently don't support any kind of formatting. Once they do, I'll make sure that if the message is an object, it is properly serialized instead.

[dblock]

This is implemented with #30. Now it can return JSON and if you hass a hash into error! it will render that.

 error!({ message => "access denied", detail => "user is missing the foobar privilege" }, 401)

[dblock]

I am closing this, please reopen if what's implemented is not sufficient.