Fixed an issue where strings were not exported correctly

This impacted all non-ASCII chars like german umlauts, eszett and french
ce cedille.
Bytearrays with UTF-8 were incorrectly re-mapped to a char array, then
written.
Updated README and removed the known issue with utf-8 strings

The issue was fixed in fd70490bb80f350a0cb2772c3421ca136e5e0238