Add kredits-formatter and additionally format balance

This adds a `balanceInt` value to the contributor data that has the
token balance formatted as full Kredits. (similar to Ether)

lib/utils/kredits-formatter.js

@@ -0,0 +1,10 @@
+const ethersUtils = require('ethers').utils;
+
+module.exports = function (value, options = {}) {
+  let etherValue = ethersUtils.formatEther(value);
+  if (options.asFloat) {
+    return parseFloat(etherValue);
+  } else {
+    return parseInt(etherValue);
+  }
+}