switched to `const` where appropriate

middleware/trimByGranularityComponent.js

@@ -1,4 +1,4 @@
-var _ = require('lodash');
+const _ = require('lodash');
 
 // This middleware component trims the results array by granularity when
 // FallbackQuery was used.  FallbackQuery is used for inputs like
@@ -13,7 +13,7 @@ var _ = require('lodash');
 // this component removes results that aren't the most granular.
 
 // layers in increasing order of granularity
-var layers = [
+const layers = [
   'venue',
   'street',
   'address',

sanitizer/_synthesize_analysis.js

@@ -1,6 +1,6 @@
-var _ = require('lodash');
+const _ = require('lodash');
 
-var fields = ['query', 'address', 'neighbourhood', 'city',
+const fields = ['query', 'address', 'neighbourhood', 'city',
     'county', 'state', 'postalcode', 'country'];
 
 function normalizeWhitespaceToSingleSpace(val) {
@@ -10,7 +10,7 @@ function normalizeWhitespaceToSingleSpace(val) {
 function sanitize( raw, clean ){
 
   // error & warning messages
-  var messages = { errors: [], warnings: [] };
+  const messages = { errors: [], warnings: [] };
 
   // collect all the valid values into a single object
   clean.parsed_text = fields.reduce( (o, f) => {