Added tests for standards_mode whereever there are tests for quirks_mode
Added rfc7319 standards_mode to the pure ruby generator and parser
Looks like this was not committed last time parser.c was generated?
Added rfc7159 standards mode to the c-extension parser and generator
Added a new EncodingError for when a string is too short to be parsed

Also:

* made the pure parser check for that, as it was the only parser that
was not checking for string length.
* made rfc7159 standards mode insist on one octet (not two), as that is
  the length of the minimum viable json value