The TM1637 board you have has quite likely been manufactured with a fault. There are two chip capacitors that must be removed for it to work. Was that in the tutorial - I don't have the time to check it?
If you install the hd44780 library (and you should, it is the best I2C LCD library available) use the hd44780_I2Cexp class.
He just plugged it into the Arduino. I didn't see any chip capacitors being removed. I bought the display from this site. Where are the two chip capacitors that need to be removed? Sorry for the big pictures, I don't know how to reduce their size.
The program semi-worked, it found the display, turned the backlight on and off and returned the same address (0x3F) that the other scanner found. On the other hand, it didn't display anything at all. It was supposed to print some text and diagnostics but the screen kept on just glowing with its backlight on.