Fix escaping in command string. (#11)

The JSON string is not supposed to be double-escaped. Only the escape characters are supposed to be double-escaped.

Support fullwidth characters.

Add command to webpage.

Fix broken image file.

Add a fallback for unsupported characters.

It's not at all great, but I don't want to deal with it.

Add error message for unsupported characters.

Remove new lines from page starts.

Also, add a new test and support the ñ character.