create TagsController to handle tags in archive and autocomplete function
Add gem taggable to sites, add possibility to add tags to sites, show tagcloud in archive
Merge branch 'master' into taggable_sites

Conflicts:
	Gemfile
	Gemfile.lock
	app/assets/javascripts/application.js
	app/assets/stylesheets/application.css
	app/views/partials/_navigation.html.haml
	app/views/sites/index.html.haml