Doc update

Paramiko is needed for sftpfs, not ftpfs

Author: lurch

docs/getting_started.rst

@@ -42,7 +42,7 @@ Prerequisites
 PyFilesystem requires at least **Python 2.6**. There are a few other dependencies if you want to use some of the more advanced filesystem interfaces, but for basic use all that is needed is the Python standard library.
 
     * Boto (required for :mod:`fs.s3fs`) https://github.com/boto/boto
-    * Paramiko (required for :class:`fs.ftpfs.FTPFS`) https://github.com/paramiko/paramiko
+    * Paramiko (required for :mod:`fs.sftpfs`) https://github.com/paramiko/paramiko
     * wxPython (required for :mod:`fs.browsewin`) http://www.wxpython.org/