Bump ruby version

.ruby-version

-2.4.2
+2.5.1

Gemfile.lock

     coffee-script-source (1.12.2)
     concurrent-ruby (1.0.5)
     daemons (1.2.4)
-    delayed_job (4.1.3)
-      activesupport (>= 3.0, < 5.2)
-    delayed_job_active_record (4.1.2)
-      activerecord (>= 3.0, < 5.2)
+    delayed_job (4.1.5)
+      activesupport (>= 3.0, < 5.3)
+    delayed_job_active_record (4.1.3)
+      activerecord (>= 3.0, < 5.3)
       delayed_job (>= 3.0, < 5)
     domain_name (0.5.20170404)
       unf (>= 0.0.5, < 1.0.0)
       tilt
     http-cookie (1.0.3)
       domain_name (~> 0.5)
-    i18n (0.8.1)
+    i18n (0.9.5)
+      concurrent-ruby (~> 1.0)
     i18n_generators (2.1.1)
       rails (>= 3.0.0)
     icalendar (2.4.1)
       mime-types-data (~> 3.2015)
     mime-types-data (3.2016.0521)
     mini_portile2 (2.1.0)
-    minitest (5.10.1)
+    minitest (5.11.3)
     multi_json (1.12.1)
     multipart-post (2.0.0)
     netrc (0.11.0)
     turbolinks (5.0.1)
       turbolinks-source (~> 5)
     turbolinks-source (5.0.0)
-    tzinfo (1.2.3)
+    tzinfo (1.2.5)
       thread_safe (~> 0.1)
     uglifier (3.2.0)
       execjs (>= 0.3.0, < 3)
   yard
 
 BUNDLED WITH
-   1.16.0
+   1.16.4