Fixed part 1 links

Author: Ricardo Duarte

index.html

@@ -104,21 +104,21 @@ <h4>Part I</h4>
             control structures, functions, and documentation.
         </p>
         <ul>
-            <li><a href="https://raw.github.com/ricardoduarte/python-for-developers/master/Chapter1/Chapter1_Introduction.ipynb">
+            <li><a href="http://nbviewer.ipython.org/urls/raw.github.com/ricardoduarte/python-for-developers/master/Chapter1/Chapter1_Introduction.ipynb">
                 Chapter 1: Introduction</a></li>
-            <li><a href="https://raw.github.com/ricardoduarte/python-for-developers/master/Chapter2/Chapter2_Syntax.ipynb">
+            <li><a href="http://nbviewer.ipython.org/urls/raw.github.com/ricardoduarte/python-for-developers/master/Chapter2/Chapter2_Syntax.ipynb">
                 Chapter 2: Syntax</a></li>
-            <li><a href="https://raw.github.com/ricardoduarte/python-for-developers/master/Chapter3/Chapter3_Control_flow.ipynb">
+            <li><a href="http://nbviewer.ipython.org/urls/raw.github.com/ricardoduarte/python-for-developers/master/Chapter3/Chapter3_Control_flow.ipynb">
                 Chapter 3: Control Flow</a></li>
-            <li><a href="https://raw.github.com/ricardoduarte/python-for-developers/master/Chapter4/Chapter4_Loops.ipynb">
+            <li><a href="http://nbviewer.ipython.org/urls/raw.github.com/ricardoduarte/python-for-developers/master/Chapter4/Chapter4_Loops.ipynb">
                 Chapter 4: Loops</a></li>
-            <li><a href="https://raw.github.com/ricardoduarte/python-for-developers/master/Chapter5/Chapter5_Types.ipynb">
+            <li><a href="http://nbviewer.ipython.org/urls/raw.github.com/ricardoduarte/python-for-developers/master/Chapter5/Chapter5_Types.ipynb">
                 Chapter 5: Types</a></li>
-            <li><a href="https://raw.github.com/ricardoduarte/python-for-developers/master/Chapter6/Chapter6_Functions.ipynb">
+            <li><a href="http://nbviewer.ipython.org/urls/raw.github.com/ricardoduarte/python-for-developers/master/Chapter6/Chapter6_Functions.ipynb">
                 Chapter 6: Functions</a></li>
-            <li><a href="https://raw.github.com/ricardoduarte/python-for-developers/master/Chapter7/Chapter7_Documentation.ipynb">
+            <li><a href="http://nbviewer.ipython.org/urls/raw.github.com/ricardoduarte/python-for-developers/master/Chapter7/Chapter7_Documentation.ipynb">
                 Chapter 7: Documentation</a></li>
-            <li><a href="https://raw.github.com/ricardoduarte/python-for-developers/master/ExercisesI/ExercisesI.ipynb">
+            <li><a href="http://nbviewer.ipython.org/urls/raw.github.com/ricardoduarte/python-for-developers/master/ExercisesI/ExercisesI.ipynb">
                 Exercises I</a></li>
         </ul>