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>

Gemfile

@@ -121,7 +121,7 @@ gem 'whenever'
 gem 'listen'
 
 # pin SASS - CUL linux hosts can't yet compile sassc
-gem 'bootstrap-sass',  '~> 3.3.0'
+gem 'bootstrap-sass',  '~> 3.4.1'
 
 # Javascript runtime, as a gem, doesn't depend on OS environment
 gem 'therubyracer'

Gemfile.lock

@@ -81,9 +81,9 @@ GEM
       blacklight (>= 6.0.2)
       jquery-rails
       rails (>= 3.0)
-    bootstrap-sass (3.3.7)
+    bootstrap-sass (3.4.1)
       autoprefixer-rails (>= 5.2.1)
-      sass (>= 3.3.4)
+      sassc (>= 2.0.0)
     builder (3.2.4)
     cancancan (2.3.0)
     capistrano (3.17.0)
@@ -350,6 +350,8 @@ GEM
       sprockets (>= 2.8, < 4.0)
       sprockets-rails (>= 2.0, < 4.0)
       tilt (>= 1.1, < 3)
+    sassc (2.4.0)
+      ffi (~> 1.9)
     spring (4.0.0)
     sprockets (3.7.2)
       concurrent-ruby (~> 1.0)
@@ -395,7 +397,7 @@ DEPENDENCIES
   binding_of_caller
   blacklight
   blacklight_range_limit
-  bootstrap-sass (~> 3.3.0)
+  bootstrap-sass (~> 3.4.1)
   capistrano
   capistrano-bundler
   capistrano-passenger