Add counter for "browser" fallback usage

Helps with #63

server/middleware/utils/incrementCounter.js

@@ -0,0 +1,15 @@
+const db = require('../../RedisClient')
+
+function incrementCounter(counter, key, by) {
+  return new Promise((resolve, reject) => {
+    db.hincrby(counter, key, by, (error, value) => {
+      if (error) {
+        reject(error)
+      } else {
+        resolve(value)
+      }
+    })
+  })
+}
+
+module.exports = incrementCounter