Add the code to initialize the (x,y,max_z) while loading the cfg
file.But seems the requests lib now broke down. Try to figure out.
The previous commit has no issue, just because the tile image at the
edge of China only have 13 zoom level, and the code need to optimize to
skip the repeatable useless trying from level 21 to 13.
Add a new config file wuhan.cfg. It's a small one which could fetch for
now.
Add some proceeding print code.
Optimize the proceed accuracy.