Fix up book links in index.html

Author: hollasch

index.html

@@ -10,15 +10,15 @@
 
 <div class='books'>
 
-  <a href='https://raytracing.github.io/InOneWeekend/'>
+  <a href='books/RayTracingInOneWeekend.html'>
     <img src='images/RTOneWeekend.jpg' width='234' height='375' alt='Ray Tracing: In One Weekend'>
   </a>
 
-  <a href='https://raytracing.github.io/TheNextWeek/'>
+  <a href='books/RayTracingTheNextWeek.html'>
     <img src='images/RTNextWeek.jpg' width='234' height='375' alt='Ray Tracing: The Next Week'>
   </a>
 
-  <a href='https://raytracing.github.io/TheRestOfYourLife/'>
+  <a href='books/RayTracingTheRestOfYourLife.html'>
     <img src='images/RTRestOfYourLife.jpg' width='234' height='375' alt='Ray Tracing: The Rest Of Your Life'>
   </a>