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
Merge pull request #135 from Erethon/feature-cheatsheets-updates

Add some new examples