Update sprockets, cut version 2.3.1

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Version 2.3.1
+
+*July 5, 2018*
+
+- Update `sprockets` in `Gemfile.lock` to fix security warnings
+
 ## Version 2.3
 
 *July 5, 2018*

Gemfile.lock

@@ -17,7 +17,7 @@ GEM
     coffee-script-source (1.12.2)
     compass-import-once (1.0.5)
       sass (>= 3.2, < 3.5)
-    concurrent-ruby (1.0.4)
+    concurrent-ruby (1.0.5)
     contracts (0.13.0)
     dotenv (2.2.0)
     erubis (2.7.0)
@@ -91,7 +91,7 @@ GEM
       activesupport (>= 3.1)
     parallel (1.10.0)
     public_suffix (2.0.5)
-    rack (2.0.1)
+    rack (2.0.5)
     rb-fsevent (0.9.8)
     rb-inotify (0.9.8)
       ffi (>= 0.5.0)
@@ -99,7 +99,7 @@ GEM
     rouge (2.0.7)
     sass (3.4.23)
     servolux (0.12.0)
-    sprockets (3.7.1)
+    sprockets (3.7.2)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)
     thor (0.19.4)
@@ -126,4 +126,4 @@ RUBY VERSION
    ruby 2.3.3p222
 
 BUNDLED WITH
-   1.14.5
+   1.15.4