Avoid using flume::Receiver::into_stream() to avoid memory leaks until the issue is resolved upstream (#394)

* Tweak rolling_total test to also confirm capacity doesn't go nuts

* Use Jemalloc

* Avoid flume's into_stream and use a workaround for now

* cargo fmt

* Improve comments now that there's an issue to point to

backend/common/src/lib.rs

@@ -28,6 +28,7 @@ pub mod ws_client;
 mod assign_id;
 mod dense_map;
 mod either_sink;
+mod flume_recv_stream;
 mod mean_list;
 mod most_seen;
 mod multi_map_unique;
@@ -37,6 +38,7 @@ mod num_stats;
 pub use assign_id::AssignId;
 pub use dense_map::DenseMap;
 pub use either_sink::EitherSink;
+pub use flume_recv_stream::{flume_receiver_into_stream, FlumeRecvStream};
 pub use mean_list::MeanList;
 pub use most_seen::MostSeen;
 pub use multi_map_unique::MultiMapUnique;