ci: intro-to-cpp: Move program impl chapters after functions and classes (#21)

Details from the functions and classes chapters are useful when implementing the calculator project.

Author: secmancer

ci/intro-to-cpp/index.html

@@ -88,18 +88,18 @@ <h3 id="Chapter_5_-_Errors">Chapter 5 - Errors</h3>
     <p>p. 169: Optional 12, 13</p>
     <p>For exercise 2, provide a working implementation with comments
     describing how each part was fixed.</p>
-    <h3 id="Chapter_6_-_Writing_a_Program">Chapter 6 - Writing a Program</h3>
-    <p>p. 217: Drill</p>
-    <p>p. 218: Exercises 4-6</p>
-    <h3 id="Chapter_7_-_Completing_a_Program">Chapter 7 - Completing a
-    Program</h3>
-    <p>Just read the chapter.</p>
     <h3 id="Chapter_8_-_Technicalities.3A_Functions.2C_etc.">Chapter 8 -
     Technicalities: Functions, etc.</h3>
     <p>Just read the chapter.</p>
     <h3 id="Chapter_9_-_Technicalities.3A_Classes.2C_etc.">Chapter 9 -
     Technicalities: Classes, etc.</h3>
     <p>Just read the chapter.</p>
+    <h3 id="Chapter_6_-_Writing_a_Program">Chapter 6 - Writing a Program</h3>
+    <p>p. 217: Drill</p>
+    <p>p. 218: Exercises 4-6</p>
+    <h3 id="Chapter_7_-_Completing_a_Program">Chapter 7 - Completing a
+    Program</h3>
+    <p>Just read the chapter.</p>
     <h3 id="Advanced">Advanced</h3>
     <p>Students wanting to cover more advanced topics of the C++ programming
     language should read chapters 17-21 from Part III in order. They cover data