credit based control flow for pull streams.
inspiration: http://250bpm.com/blog:22 http://hintjens.com/blog:15
connect two pull streams, but control the rate of flow between them.
A debtor "borrows" from a creditor's buffer. A debtor streams binary chunks to a creditor, when they are read from the creditor, a credit is issued to the debtor, who may stream more data.
MIT