Remove method redefined warnings

has_many definitions with "name" as singular and as plural e.g.
  has_many :welcome_posts_with_comment
  has_many :welcome_posts_with_comments
lets ruby complain with:

/vagrant/rails/activerecord/lib/active_record/associations/builder/collection_association.rb:65: warning: method redefined; discarding old welcome_posts_with_comment_ids
/vagrant/rails/activerecord/lib/active_record/associations/builder/collection_association.rb:65: warning: previous definition of welcome_posts_with_comment_ids was here
/vagrant/rails/activerecord/lib/active_record/associations/builder/collection_association.rb:75: warning: method redefined; discarding old welcome_posts_with_comment_ids=
/vagrant/rails/activerecord/lib/active_record/associations/builder/collection_association.rb:75: warning: previous definition of welcome_posts_with_comment_ids= was here