default to user collection

new posts, when no flag is specified for blog or collection, will now
default to the user collection. that is the username.

config/options.go

@@ -53,6 +53,10 @@ func Collection(c *cli.Context) string {
 	if coll := c.String("b"); coll != "" {
 		return coll
 	}
+	u, _ := LoadUser(c)
+	if u != nil {
+		return u.User.Username
+	}
 	return ""
 }