Support different context path

#50, fix the build-screen goes 404 when access ex:) `http://master.pool.dev/path/to/something` includes context path.

I also add test for `hooks.rb` with using infraspec, and serverspec. 🉐
@ainoya It seems that the system test runs by execute `test.sh` and it runs `rspec` command but there is `Rakefile`. Do you plan to switch testing to rake task?