Changing sorter() to sorted()

Thomas pointed out that Python uses sorted() for a generator like
this, which also happens to be the first name I used before deciding
that it sounded like a boolean query rather than an iterator.
Merge pull request #336 from bradcray/sorterator

First draft sorterator

[reviewed by @thomasvandoren]

This is a first draft of a sorterator -- an iterator that takes some
other iterator or iterable as input, captures it into an array, sorts
it, and yields the elements back out to the user.  The current
limitations in the implementation reflect limitations in the language:

(1) There's no particularly good way to constrain the formal type to
be an iterator or iterable;

(2) There's no particularly good way to declare the type of the
temporary array;

Also added a test that invokes the sorterator in three ways, one with
an array, two with invocations of iterators.
Merge branch 'master' of https://github.com/chapel-lang/chapel into fannkuchUnbounded