/about redirected to /about/

[Jason A. Donenfeld]

Hi folks,

All our links were already pointing to /about/, but it was still
possible to load the same content at /about. This posed a problem for
using relative links inside markdown or wiki pages. This commit adds
support for a 301 redirect:

http://git.zx2c4.com/cgit/commit/?id=d7034806a4b1279f62d606501f831dcad31798e6

Please let me know if this poses any problems.

Thanks,
Jason