Add 'shotgun' gem for faster example test.
Implement custom redirect path.
Apply custom redirect path to example. Add REDIRECT_PATH option when user run server on terminal.
Add a test for custom redirect path.
Replace all 'middleware' to 'make_middleware'. And remove it.
Merge two duplicated /oauth code to DEFAULT_REDIRECT_PATH.
Update README file. add short description about configuring custom redirect path.
Merge pull request #4 from shaynekang/feature/custom_redirect_path

omniauth-kakao 사용자는 redirect path를 customize 할 수 있습니다.