started to work on a problem: server errors
added tests for DELETE /api/todos
skip a test for /errors
removed rack-server_errors
fix tests and added problem descriptions
added hints
added reference urls to md file
add missing content-type definitions
deleted json_halt to make code complex
fixed tests
Merge pull request #58 from junsumida/problem-server-errors

Rack::ServerErrorsを使わずにrescueをバラまく