Add Unexpose Method

[jonmchan]

Add a method to unexpose an attribute.

Scenario for use:

You wish to inherit from a Grape::Entity that has more parameters exposed than the child entity should have exposed, you can simply inherit from the parent and unexpose the parameters that you don't want exposed.

Example:

class UserData < Grape::Entity
  expose :name
  expose :address1
  expose :address2
  expose :address_state
  expose :address_city
  expose :email
  expose :phone
end

class MailingAddress < UserData
  unexpose :email
  unexpose :phone
end

[dblock]

I like it. It needs a CHANGELOG and README update, please.

[jonmchan]

@dblock CHANGELOG and README updated.

[dblock]

Merged, thanks.

[jonmchan]

Thank you!