Use explicit dates with gaps and fix bugs that this uncovers

lib/sympto/pre-ovulatory.js

@@ -1,5 +1,9 @@
+import { LocalDate } from "js-joda"
+
 export default function(cycle) {
-  const fiveDayRuleDays = cycle.slice(0, 5)
+  const startDate = LocalDate.parse(cycle[0].date)
+  const fiveDayEndDate = startDate.plusDays(4).toString()
+  const fiveDayRuleDays = cycle.slice(0, 5).filter(d => d.date <= fiveDayEndDate)
   const preOvulatoryDays = getDaysUntilFertileMucus(fiveDayRuleDays)
   return {
     cycleDays: preOvulatoryDays,
@@ -7,7 +11,7 @@ export default function(cycle) {
       date: preOvulatoryDays[0].date
     },
     end: {
-      date: preOvulatoryDays[preOvulatoryDays.length - 1].date,
+      date: fiveDayEndDate
     }
   }
 }