added test cases
Merge pull request #16 from junsumida/tests-refactoring

added test cases
added 400, 404, 500 error endopoints
use haml views for error template
Merge branch 'master' into 404/500
Merge pull request #18 from junsumida/404/500

added 400, 404, 500 error endopoints
added tests for error cases
Merge pull request #19 from junsumida/404/500

[Check Please] added tests for error cases
Merge remote-tracking branch 'origin/master' into feature-add-activerecord