Calculate the matched portion of candidate hints, as emphasized in the hint list, insensitive to case.

This changes how the emphasized part of each candidate hint is calculated. With this change, matches are calculated w.r.t. an eponymous variable `lowerCaseQuery`, instead of the possibly-mixed-case `query` variable, for case-insensitive compatibility with the lower-case hints returned from the `filterAndSortArray` function. Addresses #71.