Mojo::JSON encoding and decoding of binary data "\a\b"

Hi Sebastian,

Mojo::JSON.pm appears to have incorrect mapping of the escape character "\b" to "\x07" instead of "\x08". As a result, in my use, binary data encoded by Mojo::JSON arrives at the client subtly corrupted.

I have added tests for the encoding of "\a\b" and decoding of the corresponding JSON data, and changed Mojo::JSON.pm to handle these characters correctly, as I understand the situation.

Regards,
Ian