Incorrect charset handling

[hadmut]

Hi,

the mbox gems assumes the full mbox file to be UTF-8 encoded. But if there is a mail encoded differently, e.g. ISO-8859-1 (quite common in Europe), mbox aborts with

Error invalid byte sequence in UTF-8

(A problem that probably never occurs in country which use the ASCII for regular language only.)

mbox needs to check the charset given in the header and read it appropriately (or read it as binary).