Squashed commit of the following:

commit 9ae6a9a143e33a9de058f40b402be6f5ed440c99
Author: Nestor Arocha <nesaro@gmail.com>
Date:   Sun Jan 12 08:55:27 2014 +0000

    fixed extract_alphabet test

commit 01e5238bab5c2b5aa66b4d7059f5b58694565b45
Author: Nestor Arocha <nesaro@gmail.com>
Date:   Sat Jan 11 17:58:20 2014 +0000

    added alphabet extract

commit 0d70494ed96c281a298e3f5bf944d50147add6f4
Author: Nestor Arocha <nesaro@gmail.com>
Date:   Sat Jan 11 14:09:23 2014 +0000

    refactored extract tests