Allow case insensitive completions

[dit7ya]

Currently the completions are case sensitive, it would be really nice to have completions that are case-agnostic.

If this becomes confusing, allowing it for just the first letter would be useful.
For example, even if I have a file titled Emacs, I should be able to see completions for emacs once I start typing em.

[alan-carroll]

I will be opening a PR later this week which in part will address this issue. See this topic on the discourse.

I'll see if I can't add one just for case-sensitivity then so it could possibly be merged early.