Added rand methods to Iterator.

This change adds rand methods to Iterator similar to those on List.  A single item is chosen from those iterated over with uniform probability.
Added rand methods to Iterator, second try.

This change adds rand methods to Iterator similar to those on List.
This change allows multiple elements to be selected, either allowing
or disallowing duplicates. Items are chosen from those iterated over
with uniform probability.
Removed error condition too few items error.

Took out the exception when the iterator contains fewer items than requested with rand().  Also, shuffle the results array after it's initialize with the first N items so the ordering is always randomized.
Merge pull request #9 from ataylor284/master

Added rand methods to Iterator.