Regular expression for date time format does not escape regexp sensitive characters

[abhi-patel]

The method apply regex at https://github.com/clemens/delocalize/blob/master/lib/delocalize/parsers/date_time.rb#L84 does not escape regex sensitive characters. This causes the issue where the original format contain regex sensitive characters such as '.' and hence invalid values gets parsed with invalid formats.

As seen in the screenshot, The format '%d / %m / %y'(the one with slash as separator) should have been picked up, but instead it pickup '%d . %m . %y'(with dot separator) picked up because of '.' character which in regex means anything.

this ends up in invalid date.