全文検索機能の実装

[m-yamashita]

Sunspotによる全文検索の実装。

[coveralls]

Coverage decreased (-27.3%) to 36.963% when pulling 09eb5c3 on fulltext-search into c3c42ed on develop.

[coveralls]

Coverage increased (+18.9%) to 83.089% when pulling a24dd20 on fulltext-search into c3c42ed on develop.

[m-yamashita]

実装完了、テストが通った為マージします。