strip_tags_long: use htmlpurifier to properly reformat html content

lib/htmlpurifier/library/HTMLPurifier/ConfigSchema/schema/URI.AllowedSchemes.txt

@@ -0,0 +1,15 @@
+URI.AllowedSchemes
+TYPE: lookup
+--DEFAULT--
+array (
+  'http' => true,
+  'https' => true,
+  'mailto' => true,
+  'ftp' => true,
+  'nntp' => true,
+  'news' => true,
+)
+--DESCRIPTION--
+Whitelist that defines the schemes that a URI is allowed to have.  This
+prevents XSS attacks from using pseudo-schemes like javascript or mocha.
+--# vim: et sw=4 sts=4