Added ipython test code back and extensions loading

doc/tuto_GP_regression.rst

@@ -2,10 +2,10 @@
 Gaussian process regression tutorial
 *************************************
 
-#.. ipython:: python
-#
-#    print "Hello world"
-#    X = [[1, 10], [1, 20], [1, -2]]
+.. ipython:: python
+
+    print "Hello world"
+    X = [[1, 10], [1, 20], [1, -2]]
 
 We will see in this tutorial the basics for building a 1 dimensional and a 2 dimensional Gaussian process regression model, also known as a kriging model.