Bump to v5.0.0.beta2

1. Removed `base-component.js` from `js.rb` exclusion list as it is no
   longer inlined.
2. `bundle exec rake update '[v5.0.0-beta2]'`
3. Updated version in `version.rb` and `README.md`

Author: glebm

README.md

@@ -20,7 +20,7 @@ Please see the appropriate guide for your environment of choice:
 Add `bootstrap` to your Gemfile:
 
 ```ruby
-gem 'bootstrap', '~> 5.0.0.beta1'
+gem 'bootstrap', '~> 5.0.0.beta2'
 ```
 
 Ensure that `sprockets-rails` is at least v2.3.2.

assets/javascripts/bootstrap-sprockets.js

@@ -1,4 +1,5 @@
 //= require ./bootstrap/dom/data
+//= require ./bootstrap/base-component
 //= require ./bootstrap/dom/event-handler
 //= require ./bootstrap/alert
 //= require ./bootstrap/button