make cars dynamic to load 1 to 6 cars (#114)

For lazy people like me for not having to change the page by hand every
time.
+ adding 2 more cars.

http/index.html

@@ -22,6 +22,7 @@
       <li><a href="index.html">Index</a>: This page (static)</li>
       <li><a href="hello_world.txt">A text file</a>: Simple text, to verify MIME type is ok. (static)</li>
       <li><a href="cars.html">Nice cars</a>: Stress test, loads several "large" images. Makes the chip panic and restart :( (static)</li>
+      <li><a href="cars.lua">Nice cars</a>: Stress test, loads several "large" images. Makes the chip panic and restart :( (dynamic to change number of cars)</li>
       <li><a href="counter.html">Count Requests</a>: Stress test, loads the same page over and over, counting every load. (static)</li>
       <li><a href="zipped.html">Zipped</a>: File is actually saved as zipped.html.gz. A compressed file! (static but gzipped)</li>
       <li><a href="zipped.html.gz">Zipped</a>: Same exact file as served above. Server is smart enough to treat the .gz extension correctly (static but gzipped)</li>