Say bye to bootstrap
Delete unnecessary code
Top nav bar style
Refactor avatar_tag helper
Refactor view code a little bit

Conflicts:
	app/helpers/application_helper.rb
	app/helpers/topics_helper.rb
	app/views/layouts/application.html.slim
	app/views/replies/_reply.html.slim
	app/views/topics/_social_share.html.slim
	app/views/topics/_tools.html.slim
	app/views/topics/_topic.html.slim
	app/views/topics/show.html.slim
Clean up routes
Merge branch 'bye-bootstrap' into develope
Record topic's last replier
Update active repliers upon new reply
Just admin no other roles
Refactor avatar into a module
Finish topic active participants
Merge branch 'active-repliers' into develope
Base & header style
Topic show style
Semantic simple_form & flutie
Topic replies style
Topic hit counter
Make test suit pass
Finish like topic