Minor fix to usage example, --ipv4 & -t are mutually exclusive.
Added filter (-f) to only show IPv4, IPv6, or ASN.
Merge remote-tracking branch 'origin' into filter

Conflicts:
	blockfinder
Merged filter (-f) into the relevant options via opt callback.
Document new :type option for -t and -n.
Usage examples updated
Merge pull request #55 from z05/filter

Usage example err, and filtering results