fix many internal links

Fixed a number of internal links that need to
go to the GitHub site.

Ran `make www` to perform the above.

2013/endoh4/README.md

@@ -142,7 +142,7 @@ So, try:
     ./endoh4 < endoh4.c # or ./endoh4.sh
 ```
 
-The [solids/](solids/) directory includes various solid data:
+The `solids` directory includes various solid data:
 
 - [Platonic solids](http://en.wikipedia.org/wiki/Platonic_solid)
 - [Archimedean solids](http://en.wikipedia.org/wiki/Archimedean_solid)

2013/endoh4/index.html

@@ -451,7 +451,7 @@ clang, and tcc. It should not trigger warnings with <code>-pedantic</code> and <
 <p>The shape of this code is the geometric net of a regular tetrahedron.
 So, try:</p>
 <pre><code>    ./endoh4 &lt; endoh4.c # or ./endoh4.sh</code></pre>
-<p>The <a href="solids/">solids/</a> directory includes various solid data:</p>
+<p>The <code>solids</code> directory includes various solid data:</p>
 <ul>
 <li><a href="http://en.wikipedia.org/wiki/Platonic_solid">Platonic solids</a></li>
 <li><a href="http://en.wikipedia.org/wiki/Archimedean_solid">Archimedean solids</a></li>