Update vulnerable package

Name: loofah
Version: 2.3.0
Advisory: CVE-2019-15587
Criticality: Unknown
URL: flavorjones/loofah#171
Title: Loofah XSS Vulnerability
Solution: upgrade to >= 2.3.1

Gemfile.lock

@@ -74,7 +74,7 @@ GEM
     concurrent-ruby (1.1.5)
     crack (0.4.3)
       safe_yaml (~> 1.0.0)
-    crass (1.0.4)
+    crass (1.0.5)
     database_cleaner (1.7.0)
     datetime_picker_rails (0.0.7)
       momentjs-rails (>= 2.8.1)
@@ -134,7 +134,7 @@ GEM
     kgio (2.11.2)
     launchy (2.4.3)
       addressable (~> 2.3)
-    loofah (2.3.0)
+    loofah (2.3.1)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     method_source (0.9.2)