Handle has one and accepts nil value for it

[pisaruk]

Now has_one associations will be taken into account when calling to_params in the parent model.
That allow us to save a parent model containing has_one associations.
For example:

class Person
  include Her::Model
  has_one :nick_name
  attributes :name
end

class NickName
  include Her::Model
  attributes :origin, :author, :created_at
end

p = Person.first
p.assign_attributes(name: 'José', 
  nick_name_attributes: {origin: 'high_school', author: 'Big Guy', created_at: 18.years.ago})
p.save

Besides that nil value will be accepted:

p = Person.first
p.nick_name = nil
p.save

[diegoy]

This feature is useful, is there any problem in this implementation in particular?

[hubert]

most of the code here is PRd in #262 which i've responded to the OP about. going to close this for now and wait for a few small changes before we try to merge it.

thanks for contributing!