Updated sprockets version per GitHub warning.

Author: gsrohde

Gemfile.lock

@@ -220,7 +220,7 @@ GEM
     selenium-webdriver (3.11.0)
       childprocess (~> 0.5)
       rubyzip (~> 1.2)
-    sprockets (3.7.1)
+    sprockets (3.7.2)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)
     sprockets-rails (3.2.1)