function getData() {
                var chunk = process.stdin.read();
                if (chunk !== null) {
                    // Remove self from stdin and call callback
                    process.stdin.removeListener('readable', getData);
                    resolve(chunk.trim());
                }
            }
Gets a string from stdin and returns a promise resolved with the string.
Note: stdin is read when the user presses 'Enter'.
Returns a promise that is resolved with the trimmed user input.