Merge pull request adafruit#27 from lcafaro/master

minor command fix

Author: ladyada

README.md

@@ -10,7 +10,7 @@ Currently the library is only tested with Python 2.6/2.7.
 For all platforms (Raspberry Pi and Beaglebone Black) make sure your system is able to compile Python extensions.  On Raspbian or Beaglebone Black's Debian/Ubuntu image you can ensure your system is ready by executing:
 
 ````
-apt-get update
+sudo apt-get update
 sudo apt-get install build-essential python-dev
 ````