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/grep

@@ -10,6 +10,13 @@ grep -R pattern folder
 # Getting pattern from file (one by line):
 grep -f pattern_file file
 
+# Find lines NOT containing pattern
+grep -v pattern file
+
+# You can grep with regular expressions
+grep "^00" file  #Match lines starting with 00
+grep -E "[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}" file  #Find IP add
+
 # Find all files who contain {pattern} in the directory {directory}.
 # This will show: "file:line my research"
 grep -rnw 'directory' -e "pattern"