add cheatsheet for df iwconfig ls and rm
Add a troubleshooting section (python 2.6 doesn't comes with the argparse module)
Add cheatsheets
Cheatsheets: minor tweaks

Made minor changes to the ls and rm cheatsheets.
Merge pull request #110 from TiTi/master

Add cheatsheets (lsof, netstat, nmap, pdftk, ps, sam2p [new])