adds SQLite database support for caching ngrams

Squashed commit of the following:

commit e03fb18822c2fe489932861a08e6363bc0d19093
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Sun May 18 17:58:12 2014 -0400

    adds sqlalchemy for model storage

commit d5d17d7195c9cdc902150975144b379a6e0ed3dc
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Sun May 18 16:23:45 2014 -0400

    terser returns

commit 271b57b7154aa48b0dd873f87618fc628c6e5607
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Sun May 18 16:18:16 2014 -0400

    adds comments

commit 2538178b468dcaf350528d68246eadef6e81c646
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Sun May 18 16:10:53 2014 -0400

    working ngram return

commit 6749c9f4c0109ae2739ad24bc100554e728aabd7
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Sun May 18 15:43:49 2014 -0400

    successful line parse

commit 9ab1da9fff3c115f21b0fa9e65c39b8944b04a93
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Sun May 18 15:40:34 2014 -0400

    fleshes out Ngram class

commit ce9fc5894788812a46e07e738437bd9e45141e7b
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Sun May 18 15:32:00 2014 -0400

    starts Ngram class

commit 268a2514e370da77f1a382abfe593929ff99ba2d
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Sun May 18 15:29:57 2014 -0400

    adds script to retrieve ngrams from flat LM file