fix the spec:
 - single quotes are special characters -- they can't begin
   unquoted values
 - newlines are not allowed in single- or double-quoted strings
 - double-quoted strings may contain double quotes, if they're not
   followed by whitespace

add these features to the implementation, and error reporting
  for newlines and missing close quotes

add tests for these features, and for error reporting

also:  add some tests for parsing data blocks