Update and some new examples

* Update a mistake in ifconfig
* Add example for a SOCKS proxy in ssh
* Add an example for mounting a NFS dir in mount
* Add a description for git blame
* Add some examples in grep
* Add example for specifing an interface in dhclient
* Add a description for apt-get install
* Add some commands in apt-cache
* Add an example of pretty printing jsons using python

cheatsheets/mount

@@ -3,3 +3,6 @@ mount -o remount,rw /
 
 # To mount Usb disk as user writable:
 mount -o uid=username,gid=usergroup /dev/sdx /mnt/xxx
+
+# To mount a remote NFS directory
+mount -t nfs example.com:/remote/example/dir /local/example/dir