clearDisplay hardcoded for 4 digits

[ja518]

While most functions use the number of digits specified in DIGITS, clearDisplay writes 0x7f only to digits 0x00~0x03.
This creates artifacts when the number of digits is bigger than 4.

--> Replaced with:
void TM1637::clearDisplay(void) {
for (int i = 0; i < DIGITS; i++) {
display(i,0x7f);
}
}

[ackPeng]

@ja518 Thank you very much, this is a good suggestion. Do you have any other problems?

[Lesords]

Hello,

I'm going to close this issue, feel free to re-open it if you have any other questions.

[Autocommentary]