Replace render calls with render_markdown helper

Gemfile.lock

app/controllers/answers_controller.rb

app/controllers/posts_controller.rb

app/controllers/questions_controller.rb

app/controllers/users_controller.rb

app/helpers/application_helper.rb

app/views/answers/edit.html.erb

app/views/categories/index.html.erb

app/views/categories/show.html.erb

app/views/comments/_comment.html.erb

app/views/layouts/_sidebar.html.erb

app/views/posts/_form.html.erb

app/views/questions/edit.html.erb

app/views/questions/new.html.erb

app/views/questions/new_meta.html.erb

app/views/search/search.html.erb