Added the ability to switch off indentation linting (issue #988)

This is a possible approach for switching off indentation linting (see #988) by setting the `indent` option to `0`. There may be a nicer way to handle this, so it's only a suggestion.

In particular, it may be preferable to handle all of the options in the `numvals` array in this way, in which case a more generic approach could be taken.