Enabling case insensitive file handling by default

Plug-ins that don't fully embrace the dynamic file expansion don't provide any nice way of telling their patterns to ignore case when on Windows. This will ensure the default options for those plugins (i.e. eslint-grunt) will automagically use case insensitive search.

I know the extra ?: operator makes this line a bit of a kludge, but wanted to submit the issue with an example of the workaround.  Happy to refine further if you wish.