Initial version
Siimplified groupBy and removed factory classes.
Added a test for Enumerable
Fixed bug in reverse list iterator.
Added test for select
Added test for projection.
Added where tests
Added some comments.
Added a version of select which provides the element index.
Added tests for any and all.
See previous comment.
Added skip method.
Added some comments.
Added tests for trees, skip, and buffer.
Added distinct
Added sort.