Proper bootstrap version and hooking

Gemfile

 gem 'bcrypt', '~> 3.1.7'
 
 # Use Bootstrap for CSS
-gem 'bootstrap-sass', '~> 2.3.0'
+gem 'bootstrap-sass', '~> 3.3.6'
 gem 'autoprefixer-rails'
 
 # Use Capistrano for deployment

Gemfile.lock

     autoprefixer-rails (6.5.3.1)
       execjs
     bcrypt (3.1.11)
-    bootstrap-sass (2.3.2.2)
-      sass (~> 3.2)
+    bootstrap-sass (3.3.7)
+      autoprefixer-rails (>= 5.2.1)
+      sass (>= 3.3.4)
     builder (3.2.2)
     byebug (9.0.6)
     coffee-rails (4.2.1)
 DEPENDENCIES
   autoprefixer-rails
   bcrypt (~> 3.1.7)
-  bootstrap-sass (~> 2.3.0)
+  bootstrap-sass (~> 3.3.6)
   byebug
   coffee-rails (~> 4.2)
   jbuilder (~> 2.5)

app/assets/javascripts/application.js

 //= require jquery
 //= require jquery_ujs
 //= require turbolinks
+//= require bootstrap-sprockets
 //= require_tree .

app/assets/stylesheets/application.css

  * files in this directory. Styles in this file should be added after the last require_* statement.
  * It is generally better to create a new file per style scope.
  *
- *= require_tree .
- *= require_self
  */
+@import "bootstrap-sprockets";
+@import "bootstrap";