super basic auth

Not sure if this is the correct way of doing this, but this is the idea I had for managing potential changes:

* Do work in new branch ('review' was a little too general here)
* Push full (new) branch to origin
* Create pull request (?)
* Do code review
* Update, commit updates to branch, merge into master, commit to origin master

In terms of this specific pull request -- this is my very (very) basic attempt at authentication. Authentication, that is, that does not hit any sort of backend DB, but merely accepts all logins and allows one to view their username!
*Flash* messages work like they do in Python (at least like they do in Flask) -- flash messages are one-time messages sent to the view (use cases include a message like "Invalid username!" which the server could send back to the login page after authentication fails).