Posts, tags & search Functionality
- Added ability for user to create posts w/ tags
- Ensured only signed-in users could create posts
- Made so tag could only exist once for post and in model
- Added before save callback on tag to downcase name
- Created new pages for posts
  - Create new post form
  - Edit existing post form
  - View post page
- Enabled search functionality on homepage
- Seeded database with random users, posts and tags
- Updated migration to include user reference in posts table