Creating a new demo app.

See http://ruby.railstutorial.org/chapters/a-demo-app
Update for demo_app Gemfile
Scaffolding users and microposts resources.
Create new sample_app.

See: http://ruby.railstutorial.org/chapters/static-pages
Updates to sample_app Gemfile
Dynamically create secret_token.
Remove `.secret` and other files from repo.