[#41] Add github hook

To create github repository and execute api call to github I used HTML
form to avoid javascript in our simple web interface. In this way we
have proper rest interface for API.

I changed also meaning name of repository. When we try to create hook
github API expect that repository name will be kind of full name:

   Example:
      name      => "lint"
      full_name => "X8/lint"

I also changed repositories reader from ListGithubRepositoriesUsecase.
In our simple web interface we can recognize that hook is alreay created
or not. This can be changed when we introduce real API where we can
provide proper information for frontend.