Use regexp for hostgroup matching

[joegreen88]

It would be awesome if we could use regexp instead of simple string matching on hostgroups here: https://github.com/smrtr/HaltoRouter/blob/master/src/Smrtr/HaltoRouter.php#L286

We could use an @ symbol at the beginning of the string to denote a regular expression.

This would allow us to define hostgroups like so:

• Group[] = "area.mysite.domain" checked normally
• Group[] = "@/area\.mysite\.([a-zA-Z0-9]+)\.domain/" checked as a regular expression