Revert "Revert "combine: add _pipeline so errors will be handled""
pipeline_of_streams: avoid recursing on stream itself if returned by _pipeline
test/errors: test that _pipeline can return the stream itself
0.10.8
Merge pull request #61 from Clever/revert-60-revert-59-combine-error-handling

Revert "Revert "combine: add _pipeline so errors will be handled""