Please, update the wiki page with key expiration explanation

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Open https://code.google.com/p/memcached/wiki/NewProgramming#Expiration
2. Read an explanation about the key expiration time (up to 30 days)
3. Be confused

What is the expected output? What do you see instead?
Complete the sentence:
Expiration times can be set from 0, meaning "never expire", to 30 days in 
seconds (i.e. 60*60*24*30).


What version of the product are you using? On what operating system?
1.4.13 Linux Debian 7

Please provide any additional information below.
https://github.com/memcached/memcached/blob/master/doc/protocol.txt

Original issue reported on code.google.com by grigory....@gmail.com on 26 May 2015 at 6:22