Fix for nullifying assocatiation ID attribute

Setting the ID attribute of an nested has-one association should set
that association to null as well.
Try node 0.10.26 on travis
Merge pull request #87 from zendesk/shajith/nullable

Fix for nullifying assocatiation ID attribute
Merge branch 'master' into josh/do_not_share_internal_data

Conflicts:
	spec/javascripts/associationsSpec.js