creates nltk role

Squashed commit of the following:

commit a5a0d052239f7f0cd525098b18d7dc1bd45648dd
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Wed Jul 2 22:54:44 2014 -0400

    fixes downloading commands

commit c3f8b17838e804f36ef905a85d35fb814b2633fc
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Sun Jun 29 19:02:54 2014 -0400

    adds docs for download not working

commit 58dc0b209d43fa103be0184efec8765a89dc4d38
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Sun Jun 29 18:50:51 2014 -0400

    fixes typo: "yaml-dev" -> "libyaml-dev"

commit e117e9ad6407825bc399dccb51a0a6d27e588393
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Sun Jun 29 18:44:05 2014 -0400

    adds yaml-dev package

commit eb9a7a0019deab828cbe9e88580e33fcc02cf3cd
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Sun Jun 29 18:30:19 2014 -0400

    fixes formatting for multiple vars_files

commit bd8a5dd8637096c66b18fb0ef6964a6a298ff9b6
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Sun Jun 29 18:26:46 2014 -0400

    adds downloading of punkt tokenizer

commit b0e87b6a5ccc358b89930d4bbae370c5af38f24f
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Sun Jun 29 18:25:58 2014 -0400

    removes nltk var from srilm config

commit 6b8dfd5aefed580e368a906a72b1e6175504a4f4
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Sun Jun 29 18:23:07 2014 -0400

    creates nltk vars

commit 677a2cf3ddd84415326b265fdc40443501504d3e
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Sun Jun 29 18:20:15 2014 -0400

    adds corpora downloading kinda

commit 02cf406461687a53f34acaab78e4ce2429b158f3
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Sun Jun 29 18:11:55 2014 -0400

    skeleton for nltk role
fixes typo in srilm_path var
adds ansible to README
trims README
enables all roles