avoid sending content past the last token during batching / batched streaming

[aniketmaurya]

Find a way to avoid sending a lot of tokens past the last token for a particular item in the batch (i.e. we need to trim past the EOS in encode_response, let's open an issue and create an example about it)

          as a more immediate improvement, we need to find a way to avoid sending a lot of tokens past the last token for a particular item in the batch (i.e. we need to trim past the EOS in `encode_response`, let's open an issue and create an example about it)

Originally posted by @lantiga in #55 (comment)