Bump up Purifier version

Author: technicalguru

composer.json

@@ -16,7 +16,7 @@
 		"php" : ">=7.0.0",
 		"ext-mbstring" : "*",
 		"technicalguru/i18n" : "~1",
-        "ezyang/htmlpurifier":"^4.13"
+        "ezyang/htmlpurifier":"^4.15"
 	},
 	"autoload" : {
 		"psr-4" : {