Display the load error, if available

nodejs-tests/compareImages.test.js

@@ -34,6 +34,6 @@ describe('compareImages', () => {
       fs.readFileSync('./demoassets/People.jpg'),
       'bogus data'
     );
-    await expect(promise).rejects.toMatch('Image load error.');
+    await expect(promise).rejects.toMatch('Error: error while reading from input stream');
   });
 });

nodejs-tests/resemble.test.js

@@ -64,7 +64,7 @@ describe('resemble', () => {
         .onComplete(function(data) {
           // console.info('Reached oncomplete for request_404');
           // console.log(data);
-          expect(data.error).toEqual('Image load error.');
+          expect(data.error).toEqual('Error: error while reading from input stream');
           resolve();
         });
     });

resemble.js

@@ -190,9 +190,9 @@ URL: https://github.com/Huddle/Resemble.js
 				hiddenImage.setAttribute('crossorigin', 'anonymous');
 			}
 
-			hiddenImage.onerror = function () {
+			hiddenImage.onerror = function (err) {
 				hiddenImage.onerror = null; //fixes pollution between calls
-				images.push({ error : "Image load error."});
+				images.push({ error : err ? err + "" : "Image load error" });
 				callback();
 			};