MeidoBot: Add failure mode for long graphemes
MeidoBot: Add failure mode for long graphemes

When considering the problem of graphemes that happen to take more bytes
to encode in UTF-8 than the given `maxByteCount` three possible failure
modes were apparent to me:
1) Skip over grapheme
2) Truncate grapheme
3) Throw exception

The first and third are the easiest, but since I don't expect to
encounter graphemes of such ridiculous lengths I've picked No.1 for now.
If I wrote this for more general use I'd probably implement all three
options and have the user of the class decide which failure mode would
fit their expected use case.

Also some small code commentary changes.

IvionSauce/MeidoBot