Fixed issue desmondmorris#23 - Better callback patterns

Node standard is callback(err, data), and this patch updates the code to reflect this.

lib/twitter.js

@@ -102,7 +102,7 @@ Twitter.prototype.get = function(url, params, callback) {
 		} else {
 			try {
 				var json = JSON.parse(data);
-				callback(json);
+				callback(null, json);
 			} catch(err) {
 				callback(err);
 			}
@@ -155,7 +155,7 @@ Twitter.prototype.post = function(url, content, content_type, callback) {
 		} else {
 			try {
 				var json = JSON.parse(data);
-				callback(json);
+				callback(null, json);
 			} catch(err) {
 				callback(err);
 			}
@@ -308,7 +308,7 @@ Twitter.prototype.stream = function(method, params, callback) {
 	});
 	request.end();
 
-	if ( typeof callback === 'function' ) callback(stream);
+	if ( typeof callback === 'function' ) callback(null, stream);
 	return this;
 };
 
@@ -624,7 +624,10 @@ Twitter.prototype.userProfileImage = function(id, params, callback) {
 		this.options.access_token_secret);
 	request.on('response', function(response) {
 		// return the location or an HTTP error
-		callback(response.headers.location || new Error('HTTP Error ' +
+		if (response.headers.location) {
+			return callback(response.headers.location);
+		}
+		callback(new Error('HTTP Error ' +
 			  response.statusCode + ': ' +
 			  http.STATUS_CODES[response.statusCode]));
 	});
@@ -682,7 +685,7 @@ Twitter.prototype.getLists = function(id, params, callback) {
 		defaults.user_id = id;
 
 	params = merge(defaults, params);
-console.log(params);
+
 	var url = '/lists.json';
 	this._getUsingCursor(url, params, callback);
 	return this;
@@ -1264,7 +1267,7 @@ Twitter.prototype._getUsingCursor = function(url, params, callback) {
 		if (data[key]) result = result.concat(data[key]);
 
 		if (data.next_cursor_str === '0') {
-			callback(result);
+			callback(null, result);
 		} else {
 			params.cursor = data.next_cursor_str;
 			self.get(url, params, fetch);