Links to readings broken

Links to previous (and missing?) sections are broken. From the minesweeper project, these links result in a Not found message + a redirect. The first two I believe should point to previous sections under Full Stack Online - Ruby/Git, but the latter doesn’t seem to have a corresponding reading/exercise and seems to be a hole in the curriculum.

Thank you for pointing this bug out. Changes made to the task urls caused these to break and we will be adjusting the curriculum accordingly as soon as possible. :nerd_face: