Mod0

### New Features:

##### Models and Tests:
 * video, user, and category models and related rspec tests

##### Routes, Controllers and Views:
 * static main page at /front (pages#front)
 * registration page at /getstarted (users#new)
 * login page at /signin
 * main page listing videos by category at /home (videos#index)
 * show page for each video at /videos/{:id} (videos#show)
 * video searchbar at /videos/search (videos#search)

##### Authentication:
 * if not logged in, redirect to static main page when accessing videos/categories routes
 * if logged in, redirect to /home when accessing /front, /signin and /getstarted routes
 * client-side and server-side validation for forms

##### Styling:
 * revised alert, main header, forms, and login styling for consistency and authentication