fix topbar to work on mobile devices

The topbar, by way of JavaScript, now works
on mobile devices such as cell phones and
tablets.

Internal links for entries from 1984 thru 2015
have been adjusted.

Ran `make www` to perform the above.

TODO: Fix some color issues on topbar.

TODO: More testing!

2013/birken/README.md

@@ -458,7 +458,7 @@ always evaluate to true.
 decoding using the clever expression, `(i & 3) - 3`, which identifies pattern 3
 and 7 as longer.
 
-* The file size of [birken.c](birken.c) is a prime number.  Deleting the first
+* The file size of [birken.c](%%REPO_URL%%/2013/birken/birken.c) is a prime number.  Deleting the first
 line also produces a prime-sized program.  These properties do not qualify the
 program as a prime number generator.