Conform stream.map to FL spec and clarify stream internal properties (#2481)
Conform stream.map to FL spec and clarify stream internal properties (#2481)

* Conform stream.map to FL spec. Clarify stream internal properties.

* Streamline ignoreInitial logic, code style edit

impinball/mithril.js,MithrilJS/mithril.js,barneycarroll/mithril.js,pygy/mithril.js,lhorie/mithril.js,impinball/mithril.js,MithrilJS/mithril.js,barneycarroll/mithril.js,pygy/mithril.js,lhorie/mithril.js