* performance improvements
bash
> for i in 1 4 9 16 25 36 64 100 144 225 255; do time python3 -m hashpic 'Hashpic rocks!' --svg --shake256 --length "$i" -i; done
python3 -m hashpic 'Hashpic rocks!' --svg --shake256 --length "$i" -i 0,06s user 0,02s system 93% cpu 0,091 total
python3 -m hashpic 'Hashpic rocks!' --svg --shake256 --length "$i" -i 0,06s user 0,02s system 95% cpu 0,084 total
python3 -m hashpic 'Hashpic rocks!' --svg --shake256 --length "$i" -i 0,05s user 0,02s system 94% cpu 0,073 total
python3 -m hashpic 'Hashpic rocks!' --svg --shake256 --length "$i" -i 0,06s user 0,02s system 94% cpu 0,083 total
python3 -m hashpic 'Hashpic rocks!' --svg --shake256 --length "$i" -i 0,06s user 0,02s system 94% cpu 0,083 total
python3 -m hashpic 'Hashpic rocks!' --svg --shake256 --length "$i" -i 0,06s user 0,02s system 94% cpu 0,082 total
python3 -m hashpic 'Hashpic rocks!' --svg --shake256 --length "$i" -i 0,06s user 0,02s system 94% cpu 0,079 total
python3 -m hashpic 'Hashpic rocks!' --svg --shake256 --length "$i" -i 0,06s user 0,02s system 95% cpu 0,085 total
python3 -m hashpic 'Hashpic rocks!' --svg --shake256 --length "$i" -i 0,05s user 0,02s system 95% cpu 0,077 total
python3 -m hashpic 'Hashpic rocks!' --svg --shake256 --length "$i" -i 0,06s user 0,02s system 94% cpu 0,088 total
python3 -m hashpic 'Hashpic rocks!' --svg --shake256 --length "$i" -i 0,06s user 0,02s system 95% cpu 0,089 total