Update README.md

Author: Snigf12

README.md

@@ -13,8 +13,8 @@ The Kinect sensor used is the xBox360 Kinect Sensor - 1414
 
 1. Install Raspbian on your Raspberry Pi - https://www.raspberrypi.org/downloads/
 2. Install the OpenCV library for Python - http://www.pyimagesearch.com/2016/04/18/install-guide-raspberry-pi-3-raspbian-jessie-opencv-3/
-3. Install libfreenect to be able to use Kinect sensor - Nice tutorial -> https://naman5.wordpress.com/2014/06/24/experimenting-with-kinect-using-opencv-python-and-open-kinect-libfreenect/ AND For more information about the OpenKinect community -> https://openkinect.org/wiki/Main_Page
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+3. Install the Numpy library for python - pip install numpy
+4. Install libfreenect to be able to use Kinect sensor - Nice tutorial -> https://naman5.wordpress.com/2014/06/24/experimenting-with-kinect-using-opencv-python-and-open-kinect-libfreenect/ AND For more information about the OpenKinect community -> https://openkinect.org/wiki/Main_Page
 
 For finding spheres, this system uses the HougCircle method. If the green and orange colors are not well filtered, you can change the ranges of the colors desired, it is used the Lab colorspace.