Ensure that input factory returns array or Traversable when created from a callable

[jdreesen]

The return value from the input factory was not checked when the Collection is created from a callable. As only arrays and Traversables are valid return types, this should be checked.

Also IteratorAggregate::getIterator() must return a Traversable so we need to wrap the return value of the input factory in an ArrayIterator in case it is an array.

[DusanKasan]

Looks good. Thank you for the contribution.