Fix recursive transfers

+ fixed transerring of recursive dirs (dirlevel was sometimes miscalculated)
+ close channel on __del__
+ added support for fnmatch style transfers (filename wildcards)
+ fixed progress callback to initially trigger on byte 0 of file to make it easier to track file by file transfers (see readme)
+ markdownize readme


thanks for implementing scp.py. using it in my paramiko powered ssh class for easy scp transfers. works on win/linux.