fixed #31 bumped version to 1.10.1

Hope you don't mind me bumping the version up.
I gave it a thought and ended up with what you see because `!xhr.responseText` covers those two cases and `null` and `0`. None of the other cases is theoretically possible (even if it ever happens, we should assume it's an old browser)
This if statement is there to say "If response type is text or nothing reasonable"