Merges the streams of a stream into a single stream.
Example:
var source = new StreamController();
var merged = source
.map((word) => new Stream.fromIterable(word.split(""))
.transform(new MergeAll());
merged.listen(print);
source.add("hello"); // prints: h, e, l, l, o
source.add("world"); // prints: w, o, r, l, d
Merges the streams of a stream into a single stream.
Example: