Upgrade Prism to v1.6.0

Author: vinistock

Gemfile.lock

@@ -39,7 +39,7 @@ GEM
       prettyprint
     prettier_print (1.2.1)
     prettyprint (0.2.0)
-    prism (1.4.0)
+    prism (1.6.0)
     psych (5.2.6)
       date
       stringio