Global Shortcut for ScreenShot

[Hierosme]

It will be cool to have a global hightspeed shortcut capability to take screenshoot as describ in that issue.

helloSystem/Utilities#206

Actually helloSystem got a tiny Application for take screenshoot, but it not cover the case for hight speed screenshot.
Clearly it have no chance to have the Grab.app from utilities is cover that case.

Task description:

• Create screen shots without Grab.app.
• Press Command-Shift-3 to capture the entire screen
• Press Command-Shift-4 to capture a portion of the screen.
• The screen shot is automatically saved on the desktop as a PDF (or PNG) file.

[probonopd]

I will do it when I have some time.