Adding an invalid record to an association does not raise an error

[IdahoEv]

When you add an invalid record to a linked 'many' association, it fails to save the record, but adds it to the array anyway without raising an error. Having the unsaved record in the array can then trigger a different issue (riak-ruby-client issue #32 basho/riak-ruby-client#32) when you try to save the outer record.

This snippet reproduces the issue in 798b898:

    class InnerDoc
       include Ripple::Document
       property :foo, String
       validates_presence_of :foo
    end
    class OuterDoc
       include Ripple::Document
       many :inner_docs
    end
    o_d = OuterDoc.new
    i_d = InnerDoc.new(:foo => nil)
    o_d.inner_docs << i_d       

No exception is raised, but after the above code is run, the following are true:

i_d.valid? == false
o_d.inner_docs == [ i_d ]
i_d.key == nil