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

@@ -136,7 +136,7 @@ gem 'sass-rails', '~> 5.0'
 gem 'coffee-rails'
 gem 'uglifier'
 # pin to 3.3, because 3.4 requires sassc, which won't build on our CenTOS 6 VMs
-gem 'bootstrap-sass', '~> 3.3.0'
+gem 'bootstrap-sass', '~> 3.4.1'
 
 # Best Bets CRUD externalized
 # # JSON APIs, for Best Bets, etc.

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 (4.2.0)
     builder (3.2.4)
     byebug (11.1.3)
@@ -383,6 +383,8 @@ GEM
       sprockets (>= 2.8, < 4.0)
       sprockets-rails (>= 2.0, < 4.0)
       tilt (>= 1.1, < 3)
+    sassc (2.4.0)
+      ffi (~> 1.9)
     scrub_rb (1.0.1)
     signet (0.14.0)
       addressable (~> 2.3)
@@ -461,7 +463,7 @@ DEPENDENCIES
   blacklight (~> 6.10.0)
   blacklight-marc
   blacklight_range_limit
-  bootstrap-sass (~> 3.3.0)
+  bootstrap-sass (~> 3.4.1)
   browser
   byebug
   cancancan