Handle network disconnections when saving files

[https://me.yahoo.com/postrockrob#52e3a]

Attempting to save an sftp file after the server machine was rebooted results in:

Traceback (most recent call last):
  File "/home/rob/src/peppy/peppy/lib/multikey.py", line 1598, in OnMenu
    self.foundMenuAction(evt)
  File "/home/rob/src/peppy/peppy/lib/multikey.py", line 1645, in foundMenuAction
    processed = self.processMultiKey(evt, keystroke)
  File "/home/rob/src/peppy/peppy/lib/multikey.py", line 1501, in processMultiKey
    self.doKeystroke(action, evt)
  File "/home/rob/src/peppy/peppy/lib/multikey.py", line 1306, in doKeystroke
    action.actionKeystroke(evt, multiplier=multiplier)
  File "/home/rob/src/peppy/peppy/actions/__init__.py", line 518, in actionKeystroke
    self.action(0, multiplier)
  File "/home/rob/src/peppy/peppy/mainmenu.py", line 367, in action
    def isEnabled(self):
  File "/home/rob/src/peppy/peppy/fundamental.py", line 234, in save
    success = MajorMode.save(self, url)
  File "/home/rob/src/peppy/peppy/major.py", line 983, in save
    self.buffer.save(url)
  File "/home/rob/src/peppy/peppy/buffers.py", line 547, in save
    fh = self.stc.openFileForWriting(saveas)
  File "/home/rob/src/peppy/peppy/stcbase.py", line 290, in openFileForWriting
    return vfs.open_write(url)
  File "/home/rob/src/peppy/peppy/vfs/utils.py", line 172, in open_write
    if exists(ref):
  File "/home/rob/src/peppy/peppy/vfs/itools/vfs/vfs.py", line 33, in exists
    return cwd.exists(reference)
  File "/home/rob/src/peppy/peppy/vfs/itools/vfs/folders.py", line 60, in exists
    return fs.exists(reference)
  File "/home/rob/src/peppy/peppy/vfs/sftp.py", line 204, in exists
    return newref
  File "/home/rob/src/peppy/peppy/vfs/sftp.py", line 189, in _stat
    return client
  File "build/bdist.linux-x86_64/egg/paramiko/sftp_client.py", line 337, in stat
  File "build/bdist.linux-x86_64/egg/paramiko/sftp_client.py", line 628, in _request
  File "build/bdist.linux-x86_64/egg/paramiko/sftp_client.py", line 660, in _read_response
SSHException: Server connection dropped: