Map a co generator stream over a function.
var read = map(stream(), function*(data, i){
return i + ': ' + data;
});
var data;
while (data = yield read()) console.log(data);
Call fn with each value read yields, plus its iteration index, and yield
the return value.
A falsy return yields skips a value and doesn't end the stream.
read can also be an Array.
$ npm install co-map
MIT