Make dots other punctuation optional in fromString

[icambron]

DateTime.fromString is very picky about parsing. A month name has to exactly match what Luxon expects:

DateTime.fromString('févr.', 'MMM', { locale: 'fr'}).isValid //=> true
DateTime.fromString('Févr.', 'MMM', { locale: 'fr'}).isValid //=> true
DateTime.fromString('fevr.', 'MMM', { locale: 'fr'}).isValid //=> false
DateTime.fromString('févr', 'MMM', { locale: 'fr'}).isValid //=> false

I'm not sure how to desensitize the accents (or if that is even desirable), but I think the dots ought to be optional. Should be easy enough to inject ? into the regexes before trying them.

[icambron]

The fix for dots is in d1c67b1. Going to ignore other punctuation and accent stuff for now.