Add support for case insentivity in glob search pattern

[biggert]

Note that this allows for a global mode modifier at the beginning of the pattern. It does not add support for individual mode modifiers scatterred throughout the pattern.

[biggert]

I'll admit to this being a bit primitive. I'm not emotionally connected to the way this was implemented... I just need this feature ASAP so feel free to do it in a better way if possible.

[noprompt]

I'm not sure how others would feel, but if it were me ignore-case? would be an explicit option (ie. :ignore-case? true) instead of a silent one. That would make the API clear and remove the parsing step.

[biggert]

I can't disagree with that... my initial approach was to use an option! I was conflicted though because regular expressions support this functionality within them and since this function takes a regular expression, I felt like that might be a more natural place for regex experts to use it... but myself being a light user of regex, I would agree that having an explicit argument is certainly a valid alternative.

[Raynes]

I really don't want to do much of anything else to the glob stuff. It's really not a great idea to even have that thing. In my experience, if you're using this half-assed implementation of globs you should probably be using a real shell instead.

Thanks for the pull request though! If I add any new features to the glob function this will be one of them. Doubt that's going to happen though.