* Ignore `cargo tarpaulin` output files
* Add expected result for `columns` example
Examples without provided expected output will never be tested.
The subset of commands available in `test_examples()` is limited thus
excluding the tests depending on other commands
* Add example test harness to `reject`
* Test and fix `wrap` example
* Test and fix `drop column` example
* Update `from ods` examples
* Update `from xlsx` examples
* Run `to nuon` examples
* Run `hash base64` examples
* Add example output to `path parse`
* Test and fix the `grid` examples
