Add helper for using highcharter / Highcharts more easily

Change-Id: I9c4d501aebcc31cf997ef4e572d107a4aa083325
diff --git a/NAMESPACE b/NAMESPACE
index 8a84580..096d676 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -10,6 +10,7 @@
 export(geom_freq_by_year_ci)
 export(ggplotly)
 export(group_by)
+export(hc_freq_by_year_ci)
 export(ipm)
 export(mutate)
 export(percent)
@@ -34,6 +35,7 @@
 exportMethods(persistAccessToken)
 exportMethods(show)
 import(R.cache)
+import(highcharter)
 import(httr)
 import(keyring)
 import(methods)