Bump bootstrap-sass from 3.3.7 to 3.4.1

Bumps [bootstrap-sass](https://github.com/twbs/bootstrap-sass) from 3.3.7 to 3.4.1.
- [Release notes](https://github.com/twbs/bootstrap-sass/releases)
- [Changelog](https://github.com/twbs/bootstrap-sass/blob/master/CHANGELOG.md)
- [Commits](twbs/bootstrap-sass@v3.3.7...v3.4.1)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Gemfile

@@ -130,7 +130,7 @@ gem 'jquery-ui-rails'
 gem 'sass-rails'
 gem 'coffee-rails'
 gem 'uglifier'
-gem 'bootstrap-sass', '~> 3.3.0'
+gem 'bootstrap-sass', '~> 3.4.1'
 
 # JSON APIs, for Best Bets, etc.
 gem 'jbuilder'

Gemfile.lock

@@ -102,9 +102,9 @@ GEM
       jquery-rails
       rails (>= 3.0)
       tether-rails
-    bootstrap-sass (3.3.7)
+    bootstrap-sass (3.4.1)
       autoprefixer-rails (>= 5.2.1)
-      sass (>= 3.3.4)
+      sassc (>= 2.0.0)
     browser (2.7.1)
     builder (3.2.3)
     byebug (11.0.1)
@@ -387,6 +387,8 @@ GEM
       sprockets (>= 2.8, < 4.0)
       sprockets-rails (>= 2.0, < 4.0)
       tilt (>= 1.1, < 3)
+    sassc (2.2.1)
+      ffi (~> 1.9)
     scrub_rb (1.0.1)
     signet (0.12.0)
       addressable (~> 2.3)
@@ -465,7 +467,7 @@ DEPENDENCIES
   blacklight (~> 6.10.0)
   blacklight-marc
   blacklight_range_limit
-  bootstrap-sass (~> 3.3.0)
+  bootstrap-sass (~> 3.4.1)
   browser
   byebug
   cancancan