Version overflow above 256

[Syndesi]

Hi,

when I use your tool with larger version numbers, I get an overflow and the version jumps back to 1:

docker run -it usvc/semver:latest bump patch 0.0.255
> 0.0.256
docker run -it usvc/semver:latest bump patch 0.0.256
> 0.0.1

I guess that it's due to using bytes internally?
To be honest I don't use those large version numbers myself, I just did some testing ^^
Great tool btw :D