object syntax to allow setting current object

[ajsharp]

This change allows you to set @current_object with the object method in order to use the attributes method in a top-level keyspace.

Person = Struct.new(:name, :age, :employer)
person = Person.new('alex', 28, 'Zaarly')

object person do
  attributes :id, :name, :employer
end

This will output the following json document:

{
  "name": "alex",
  "age": 28,
  "employer": "Zaarly"
}

[coveralls]

Coverage increased (+0%) when pulling 527f632 on set-current-object into 55a22fd on master.

[zk]

Looks great dude.