Fix 10.9 Wireless Preference Parsing

I was having issues running OSXAuditor under Mavricks. After taking a look through the Plist I realized that the ```/Library/Preferences/SystemConfiguration/com.apple.airport.preferences.plist``` file format has changed. 

I added a more robust OSX version detection based on the current ```GetAuditedSystemVersion``` method. This made it easer to create different parsing based on the different plist versions. I think this makes it more robust for future usage on 10.9.