Bump to v4.2.1

Author: glebm

README.md

@@ -17,7 +17,7 @@ Please see the appropriate guide for your environment of choice:
 Add `bootstrap` to your Gemfile:
 
 ```ruby
-gem 'bootstrap', '~> 4.1.3'
+gem 'bootstrap', '~> 4.2.1'
 ```
 
 Ensure that `sprockets-rails` is at least v2.3.2.

lib/bootstrap/version.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
 module Bootstrap
-  VERSION       = '4.1.3'
+  VERSION       = '4.2.1'
   BOOTSTRAP_SHA = '9e4e94747bd698f4f61d48ed54c9c6d4d199bd32'
 end