Add `StreamExtensions.listenAndBuffer()` (#235)

The immediate motivation for this is to buffer stderr from a subprocess until we learn whether the subprocess completed successfully or not. It's important to consume the output eagerly so the process doesn't deadlock after saturating the OS and/or `dart:io` buffers, but we don't want to print it at all if the process completes successfully.

Prepare to publish (#214)

Drop `-dev` postfix.

Deprecate the sink_base classes. (#193)

The approach was not considered a good fit for the package API,
and we'll remove the classes and consider another approach, if one is needed.

Prepare to publish (again) (#190)

I made the previous publish at a commit too early. Move the changelog
for the `StreamGroup` bug fix to a new version and prepare to publish.

Add *SinkBase classes for implementing custom sinks (#188)

Add doc comment on Stream.slices (#180)

Based on the doc comment on the unmerged Iterable.slices from
dart-archive/collection#191

Drop extra newline in changelog, sort deps, and drop `-nullsafety` from
constraints.

Fix a StreamGroup bug when a component stream's listen() throws (#173)

This would put the StreamGroup into an inconsistent state where it
would believe itself to be active, but only some streams would have
subscriptions. This was exacerbated by dart-lang/sdk#45815, which
meant that even though _onListen threw an error a StreamSubscription
was created and returned, so further callbacks could still be called.

Now instead of going into an inconsistent state, the StreamGroup
simply cancels itself.

Fix docs in FutureGroup (#171)

There is no `stream` member to reference.

Prepare to publish stable null safety (#153)