Merge pull request #33 from KazumaKobayashi/develop

たぶん、これでいけるはず（汗
Group
Merge pull request #34 from KazumaKobayashi/develop

Add EmailValidator and change models.
Merge pull request #35 from KazumaKobayashi/develop

URLパターンの実装
Merge pull request #36 from KazumaKobayashi/develop

エラーメッセージをリストに出来るように変更
Merge pull request #43 from KazumaKobayashi/develop

フレンドの登録ロジック追加とバグ修正
Merge pull request #47 from KazumaKobayashi/develop

コメントを修正
Merge pull request #48 from KazumaKobayashi/develop

ログアウト関係の追加
Group part2
Merge pull request #52 from KazumaKobayashi/master

Group関係