Merge branch 'release/0.11.3'
Use `EmrFileAccessDetails` object for passing new sftp params:
* sftp_server_port
* sftp_server_private_key
* sftp_server_private_key_pass
Use new `sfpt_server_*` params when connecting to sftp with a private key
Add unit test for connecting to sftp with a private key
Add dependency on `sftpserver` to `.travis.yml`
Merge pull request #79 from indera/fix-46-support-ppk-sftp

Fix 46 support ppk sftp