Handle more errors from pysmb

Add more exceptions caught to raise as RemoteConnectionError:
- Along with a change in miketeo/pysmb pull request #10, catch
  errno.ECONNREFUSED for a failure to connect to the SMB server.
- Catch socket.error (child) instead of IOError (parent) for
  errno.ECONNREFUSED and errno.EPIPE.
- socket.EAI_NONAME (unknown hostname).
- smb.NotConnectedError for when an attempt is made to use a
  non-existant connection.  For example, using the wrong NetBIOS name
  with a Window server.  Samba servers apparently do not care.