move roman numerals function to helpers

src/components/Header.vue

@@ -11,8 +11,7 @@
     <span v-for="(lemma, index) in lemmas" 
           :key="index">{{lemma.lemma}}<!--
           --><span :aria-label="hgno_arabic" 
-                   class="hgno" 
-                   v-if="hgno(lemma)">{{" "+hgno(lemma)}}</span><span 
+                   class="hgno">{{" "+roman_hgno(lemma)}}</span><span 
                    class="title_comma" 
                    v-if="lemmas[1] && index < lemmas.length-1">{{", "}}
                   </span>
@@ -88,13 +87,8 @@ export default {
 
   },
   methods: {
-    hgno: function(lemma) {
-      let hgint = parseInt(lemma.hgno)
-      if (hgint > 0) {
-        return ["I","II","III","IV", "V", "VI", "VII", "VIII", "IX", "X", "XI", "XII", "XIII", "XIV", "XV", "XVI"][hgint-1]
-      }
-      return ""
-    }
+    roman_hgno: helpers.roman_hgno
+
   },
   computed: {
     secondary_header_text: function() {

src/utils/helpers.js

@@ -188,4 +188,12 @@ var fraction = function(numerator, denominator) {
 
 }
 
-export default { group_list, fraction }
+const roman_hgno = function(lemma) {
+  let hgint = parseInt(lemma.hgno)
+  if (hgint > 0) {
+    return ["I","II","III","IV", "V", "VI", "VII", "VIII", "IX", "X", "XI", "XII", "XIII", "XIV", "XV", "XVI"][hgint-1]
+  }
+  return ""
+}
+
+export default { group_list, fraction, roman_hgno }