skip now returns the stream in input instead of fresh one

Pros:

  - with the previous version, skipping many elements ended up in
    stack overflow

  - with a fresh stream, the counter is set to zero, which has no real
    benefit in practice
Merge pull request #4 from pveber/skip_stack_overflow

skip now returns the stream in input instead of fresh one
update changelog
Merge pull request #5 from pveber/skip_stack_overflow

update changelog