change readAsBinaryString to readAsArrayBuffer (works in IE now) (#48)

Author: Stanislav

libs/backendless.js

@@ -3620,7 +3620,7 @@
                             reader.onerror = function(evn) {
                                 async.fault(evn);
                             };
-                            reader.readAsBinaryString(files[i]);
+                            reader.readAsArrayBuffer(files[i]);
 
                         } catch (err) {
                             filesError++;