Tarsnap: depend on Homebrew OpenSSL.

Transit requires OpenSSL. So far we’ve been linking Tarsnap to the
system-supplied OpenSSL. Doing so kind of sucks, because Apple *still*,
to my knowledge, hasn’t patched Mavericks for the vulnerabilities
disclosed in OpenSSL 0.9.8 and later fixed by 0.9.8za. We should stop
building software against the Apple provided OpenSSL generally, but
particularly for security software like Tarsnap.

Also: bumps the Homepage to the correct https link.

Formula/tarsnap.rb

@@ -1,11 +1,12 @@
 require 'formula'
 
 class Tarsnap < Formula
-  homepage 'http://www.tarsnap.com/'
+  homepage 'https://www.tarsnap.com/'
   url 'https://www.tarsnap.com/download/tarsnap-autoconf-1.0.35.tgz'
   sha256 '6c9f6756bc43bc225b842f7e3a0ec7204e0cf606e10559d27704e1cc33098c9a'
 
   depends_on 'xz' => :optional
+  depends_on 'openssl'
 
   def install
     system "./configure", "--disable-dependency-tracking",