Refactor the left bar side menu, improve tag autosuggestion design, close #4271

Changelog.md

app/assets/javascripts/app/views/aspect_view.js

app/assets/javascripts/app/views/aspects_list_view.js

app/assets/javascripts/app/views/tag_following_view.js

app/assets/stylesheets/application.css.sass

app/assets/stylesheets/sidebar.css.scss

app/assets/templates/aspect_tpl.jst.hbs

app/assets/templates/aspects-list_tpl.jst.hbs

app/assets/templates/tag_following_list_tpl.jst.hbs

app/assets/templates/tag_following_tpl.jst.hbs

app/views/aspects/_aspect_listings.haml

app/views/streams/main_stream.html.haml

app/views/tags/_followed_tags_listings.haml

app/views/tags/show.haml

config/application.rb

features/follows_tags.feature

features/manages_aspects.feature

features/mentions_from_profile_page.feature

features/step_definitions/aspects_steps.rb

features/step_definitions/custom_web_steps.rb