added autocomplete and tokeninput gems , used in letters
added letters and enabled autocomplete and tokeninput for sender and recievers
Merge branch 'master' of github.com:mahsa-poorjafari/Housing_Association

Conflicts:
	app/assets/javascripts/letters.js.coffee
	app/assets/stylesheets/letters.css.scss
	config/routes.rb
	db/schema.rb