fixed buffering triggers (#499)

* [FIX] accounting for pull request messages was happening when the iterator executed, creating additional pulls on the next message to be processed.
[FIX] tagged consumers api as beta, deprecated legacy subscribes/fetch/etc.

* making test pass

* PR comments

jetstream.md

@@ -156,6 +156,21 @@ await js.publish("a.b", Empty, { expect: { lastSubjectSequence: pa.seq } });
 
 ### Processing Messages
 
+Starting with nats-base-client (NBC) 1.14.0, a new API for consuming and
+processing messages in JetStream is available in the JavaScript clients. The new
+API is currently provided as a _preview_, and will deprecate previous JetStream
+subscribe APIs as [_legacy_](./legacy_jetstream.md). It is encouraged to start
+experimenting with the new APIs as soon as possible.
+
+The new API:
+
+- Streamlines consumer creation/updates only happen on JSM APIs (or via ordered
+  consumer operations)
+- Consuming messages requires a consumer to already exist
+- Adopts a "pull" consumer for all consumer operations, however messages are
+  presented to the client as if they were a "push" consumer.
+-
+
 Messages are processed by subscriptions to the stream. The JavaScript client
 provides several ways a consumer can read its messages from a stream.