fix: use javascript strict mode everywhere to prevent errors

Some direct global variable assignments where causing issues in older
version of Node. Using strict mode everywhere disallows that pattern,
so it's easier to spot.

src/core/logger.js

@@ -1,3 +1,5 @@
+'use strict';
+
 const winston = require('winston');
 const fs = require('fs-extra');
 const LOGFILE = __dirname + "/../ace.log";

src/http/http.js

@@ -1,5 +1,7 @@
 #!/usr/bin/env node
 
+'use strict';
+
 const express = require('express');
 const uuidv4 = require('uuid/v4');
 const multer = require('multer');

src/report/analyze-a11y-metadata.js

@@ -1,3 +1,5 @@
+'use strict';
+
 // input: json extraction of metadata
 // output: description of accessibility metadata
 /*
@@ -11,7 +13,7 @@
 
 const winston = require('winston');
 
-a11yMeta = [
+const a11yMeta = [
 "schema:accessMode",
 "schema:accessibilityFeature",
 "schema:accessibilityHazard",

src/scripts/ace-axe.js

@@ -1,5 +1,8 @@
 /* eslint-disable */
-window.daisy =  window.daisy || {};
+
+'use strict';
+
+var daisy = window.daisy =  window.daisy || {};
 daisy.ace = daisy.ace || {};
 daisy.epub = daisy.epub || {};
 

src/scripts/ace-extraction.js

@@ -1,6 +1,9 @@
 /* eslint-disable */
-window.daisy =  window.daisy || {};
-ace = daisy.ace = daisy.ace || {};
+
+'use strict';
+
+var daisy = window.daisy =  window.daisy || {};
+var ace = daisy.ace = daisy.ace || {};
 
 ace.createReport = function(report) {
     let reportData = function(field, array) {