Merge branch 'release/1.10.0'
Disable ability to create stateful mutligroup buffers and per-group prepare/cleanup (#100).
Merge branch 'release/1.10.1'
Merge remote-tracking branch 'upstream/master' into develop
Use Merge instead of GroupBy for (combine)
Merge pull request #144 from ipostelnik/combine-merge

Use Merge instead of GroupBy for (combine)