Release 2.5.1 (ESP8266/32 Mining fix)

Hey there! This update should fix the latest problems while mining on ESP8266/32 boards.

Please re-upload the codes to your boards.
Other than the corrected ESP codes, this release is the same as Release 2.5.
Have fun mining!

⚠️ NOTICE: .exe binaries may be detected as a virus by your antivirus software. This is a false positive caused by pyinstallers bootloader, read about it here. Duino-Coin is not a virus.