Bump tolk from 2.0.0 to 3.1.0

Bumps [tolk](https://github.com/tolk/tolk) from 2.0.0 to 3.1.0.
- [Release notes](https://github.com/tolk/tolk/releases)
- [Changelog](https://github.com/tolk/tolk/blob/master/CHANGELOG.md)
- [Commits](https://github.com/tolk/tolk/compare/v2.0.0...v3.1.0)

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

Gemfile

@@ -52,7 +52,7 @@ group :development do
   gem "spring"
   gem "yard"
 
-  gem 'tolk', '~> 2.0.0'
+  gem 'tolk', '~> 3.1.0'
 
   gem "bullet"
   gem "rack-mini-profiler"

Gemfile.lock

@@ -251,9 +251,10 @@ GEM
     thor (0.20.3)
     thread_safe (0.3.6)
     tilt (2.0.8)
-    tolk (2.0.0)
-      rails (>= 4.0)
+    tolk (3.1.0)
+      rails (>= 5.0)
       safe_yaml (>= 0.8.6)
+      sass
     tzinfo (1.2.5)
       thread_safe (~> 0.1)
     uglifier (4.1.17)
@@ -310,7 +311,7 @@ DEPENDENCIES
   sqlite3
   swf_fu
   therubyracer
-  tolk (~> 2.0.0)
+  tolk (~> 3.1.0)
   uglifier (>= 1.3.0)
   will_paginate
   yard