Fixed incompatibility with latest code.google.com/p/go.crypto/ssh
Update CONTRIBUTORS
Merge pull request #6 from s4uliu5/master

Fixed incompatibility with latest code.google.com/p/go.crypto/ssh
Added client methods Mkdir() extend Remove for directories

Adds the Mkdir() to create a new directory on the SFTP server and also extends
Remove() to remove directories as well.
Fixed an error in marshalUint64() that resulted in incorrect marshalling of values >= 2^24
Added function Chtimes() to modify access and modification time of a file