Add account login functionality

[Matt Murphy]

Create an admin screen protected by basic auth.

Allow accounts to be created, each account should be identified by a sha1 hash and an account name (company name, etc.).

An account should be created with one user (email address and password). Additional user accounts should be able to be created.

No need for different privileges for users. Users should be able to log in and view and edit information about their account, including training the classifier on their data.

There should be a different classifier stored for each account.

[Kazi Manzur Rashid]

Any preference for data persistence (ar, dm, mongoid) and writing tests (RSpec, MiniTest)?

[Matt Murphy]

Prefer just simple redis for persistence. Prefer minitest.