Maybe solved that windows specific problem

[bofm]

A possible solution for the problem:
"this is windows specific problem, that you cannot tell if there are more bytes ready, so we read only 1 at a times"

How it works:
read1(n) method allows us to read up to n bytes.

io.open(<popen_object>.stdout.fileno(), 'rb', closefd=False) as out:
    bytes = out.read1(4096)

[bofm]

Works fine on ST3/Windows 8.1. Noticeably faster than 1 byte at a time.

[gacelita]

Going with #307 on this one.