Implement Broker subdomain

Add simple HomeController
Install devise with Broker model
Require authenticated broker for HomeController
Get rid of require_tree in application assets
Make separate layout for Broker Tools
Install Capybara gem for feature testing
Add basic feature test for Broker Tools
Make own main menu for Broker Tool
Implement Flash Messages
Show Broker Admin only for admins
Add logout link for brokers
Make devise forms pretty
Implement Lender model
Add authorize_broker! method to BrokerController

Return 403 error if broker is not admin
Add subhead support for broker layout
Implement CRUD for lender model