Add formatted_duration()

サーバーサイドの処理を参考にしてformatted_duration()関数を追加
Add TimeEntries API and replace my api

fix #429
Refactor timer process

fix #433

オブザーバーオブジェクトを作成し、描画処理をBackbone.Viewで行う。
If select all projects, add issue button is not shown

fix #423
Remove dead code and unused file
Merge pull request #436 from kmiyake/fix_timer_code

Fix timer code
Merge pull request #440 from kmiyake/iss-423_remove_add_issue_button

Remove add issue button