Use Regex against Facts for setting default hostgroup

This change would allow the use of a regex against any given fact rather that just the hostname of the machine. 

The first match found  as listed in the config would be applied to the machine. As ruby 1.9.x retains the order of a hash read from config, this should be a reliable way of establishing the priority.

Eventually I would like to perhaps do compound comparisons (If factA = regex and FactB = regex), but this seems like a good start.

Open to any and all suggestions!
I like it. Does ruby pass the returned object up the chain?

Example:
```
      def find_match(facts_map)
        facts_map.each do |group, fact|
          return group if group_matches?(fact)
        end
      end
```

Would that pass 'group' all the way up and return it? Or do I need to return group again inside the find_match def itself?