#3 support mirror a dir from URL

[LI Daobing]

Hello,

how about support directly mirror an URL.

for example, I have an URL: http://photo.163.com/photos/tsubake/67665571/, I can get the username is tsubake, but it's hard to know that I should use 'mirror 123' to get this dir. especially when this use has many dir, and I should use many `goto next' and maybe I will miss the correct one.

Thanks.