Homepage styling. change trending photo's background color.
CSS formatting for heroku.
Changed homepage caption.
Add comments about saving tweets in database.
Create new tables for tweets and images.
App now use Tweet api only if tweet is 30 minutes or older. (now work with new tweets table.)
App now stores wiki_url to the database.
App now saves population data in to the database.
App now store images url into the database.
Delete unnecessary if condition. Change city's validation.
Simplify logic for creating city. Wiki url saving logic fix.
Merge branch 'feature'

Conflicts:
	app/controllers/cities_controller.rb
Fix bug where it displayed unvisited city when uncounted to 0.