Add sorting with :sort => true for has_many :in => :array

References bug #428.

I actually don't mind the perf hit because it's a small one (it just asks what's the id is of this element's id in this list).  Also see the rdoc documents around sort_by.  (http://ruby-doc.org/core-2.1.4/Enumerable.html#method-i-sort_by)

I've left off sorting by default.