Gemfile.lock: update loofah gem version

Version 2.2.0 has a vulnerability (CVE-2018-8048).

Author: peff

Gemfile.lock

@@ -97,7 +97,7 @@ GEM
     json (2.1.0)
     launchy (2.4.3)
       addressable (~> 2.3)
-    loofah (2.2.0)
+    loofah (2.2.2)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.0)