read_decimal_digits_into -> read_decimal_digits (#31)
read_decimal_digits_into -> read_decimal_digits (#31)

Merge uses of `read_decimal_digits` and `read_decimal_digits_into`

Since read_decimal_digits will allocate the string for us, we can just
use it to do so!

* inline read_decimal_digits_into

dherman/kora,dherman/kora,RReverser/esprit,RReverser/esprit