Changed channel to a class.

I believe this interface is better to work with. Later I'll add the
"send message" interfaces to the channel class.

src/node.cpp

@@ -31,22 +31,33 @@ node::~node() {
 	network.join();
 }
 
-void node::join_channel(const std::string &name) {
+channel *node::join_channel(const std::string &name) {
+	// don't do anything if already joined
 	if(get_channel(name))
-		return;
-	channels[name].key = dht::InfoHash::get(name);
-	channels[name].token = network.listen<struct message>(
-			channels[name].key,
-			[&](struct message &&msg) {
-				channels[name].messages.push_back(msg);
-				return true;
-			});
+		return nullptr;
+
+	channels.push_back(new channel(name, &network));
+	return channels.back();
+}
+
+channel *node::get_channel(const std::string &name) {
+	for(auto i : channels)
+	{
+		if(i->get_name() == name)
+			return i;
+	}
+	return nullptr;
 }
 
 void node::leave_channel(const std::string &name) {
-	if(not get_channel(name))
-		return;
-	network.cancelListen(channels[name].key,
-			channels[name].token.get());
-	channels.erase(name);
+	for(auto i = channels.begin();
+			i not_eq channels.end(); ++i)
+	{
+		if((*i)->get_name() == name)
+		{
+			delete *i;
+			channels.erase(i);
+			return;
+		}
+	}
 }