Check for "clear" command

Hello,

Here the "ANSI way" of clearing the screen doesn't quite work (for virtual consoles and terminal emulators alike), in the sense that it actually puts the cursor one line below the top of the screen.  Like so:
![ansi](https://cloud.githubusercontent.com/assets/2074014/5132102/a19f3412-70e0-11e4-9d07-f641b3aa6a76.png)

So I just check for clear, and use it if available, since it *really* puts the cursor at 0,0.
Just a small suggestion.

Thank you.
--
Tiago Polizelli Brait