New encrypted_cookie gem: encrypted sessions for Rack

[Christian von Kleist <cvonkleist@gmail.com>]

I've created a gem called encrypted_cookie which gives Rack encrypted,
integrity-protected session storage in cookies. (The integrity
protection is the same as the normal Rack::Session::Cookie, and the
added encryption is 128-bit AES).

I'd *really* appreciate feedback on the security of my implementation
from other Rack users. If you'd like to try it out, it's very easy to
use:

1) gem install encrypted_cookie
2) Then do this in your Rack app:

  require 'encrypted_cookie'

  use Rack::Session::EncryptedCookie,
    :secret => TYPE_YOUR_LONG_RANDOM_STRING_HERE

More information at https://github.com/cvonkleist/encrypted_cookie

Much thanks in advance to anyone who can comment on the security of
this approach!