Protect against json integer overflow

Closes #75

tests/test_json.rs

@@ -708,6 +708,7 @@ fn test_parse_number_errors() {
         ("1e", Error::SyntaxError(ErrorCode::InvalidNumber, 1, 2)),
         ("1e+", Error::SyntaxError(ErrorCode::InvalidNumber, 1, 3)),
         ("1a", Error::SyntaxError(ErrorCode::TrailingCharacters, 1, 2)),
+        ("777777777777777777777777777", Error::SyntaxError(ErrorCode::InvalidNumber, 1, 20)),
     ]);
 }