Add tests for the IPv6Address class and ensure they pass

lib/btc_wire_proto.rb

@@ -22,19 +22,25 @@ class Ipv6Address < BinData::Primitive
   end
 
   def set(v)
+    v = IPAddress(v) if v.is_a?(String)
     v = IPAddress::IPv6::Mapped.new(v.to_s) if v.is_a?(IPAddress::IPv4)
-    v = IPAddress(v.to_s) unless v.is_a?(IPAddress::IPv6)
+    if v.is_a?(Fixnum) || v.is_a?(Bignum)
+      v = if v < 2**32
+        IPAddress::IPv6::Mapped.parse_u128(v)
+      else
+        IPAddress::IPv6::parse_u128(v)
+      end
+    end
+      
 
     if v.respond_to?(:to_u128)
-      address = v.to_u128
+      self.address = v.to_u128
     else
       raise ArgumentError.new("Can't set #{v.class} to an IPv6Address")      
     end  
   end  
 end
 
-
-
 # Implementation of the BitCoin wire protocol, written using bindata.
 # Reference: https://en.bitcoin.it/wiki/Protocol_specification
 #