fio cat --ignore-errors is ignored

[geowurster]

The --ignore-errors flag for fio cat is not used. Noticed while looking at the source code - don't have an example command that highlights the issue.

[sgillies]

Let's not do anything about this for 1.6.3 and consider removing the option for 2.0. It's an accidental option.

[geowurster]

@sgillies The idea being that an error is indicative of a bad dataset rather than an issue with Fiona?