Add a Micropost model and its controller, write integration tests for both of them and have them
passing, update the _error_messages.html.erb file so that it can be generalized for use by both
model's views, fill in the views for the actions on the Microposts Controller so that they look
good and enable a user to add a new micropost through a textarea on a micropost form partial - The
app is now ready to begin section 10.3.3 (A proto-feed).