added html helper function for closing tags

ftplugin/html_snip_helper.vim

@@ -0,0 +1,10 @@
+" Helper function for (x)html snippets
+if exists('s:did_snip_helper') || &cp
+	finish
+endif
+let s:did_snip_helper = 1
+
+" Automatically closes tag if in xhtml
+fun! Close()
+	return stridx(&ft, 'xhtml') == -1 ? '' : ' /'
+endf