streams are UTF-8

[jakecoffman]

Thanks to @kriive for pointing this out in #8.

Currently the streaming is counted by bytes, but it should be counted by UTF-8 rune.

In addition to updating Parse, we need to update ReadSome. Are there any other places?

[kriive]

Yes, I guess Guacamole mostly uses ASCII (which maps to UTF-8 single byte) so it's understandable it didn't show up! Maybe if a user uses emojis in hostnames or password (oh dear...) it could cause some issues.