Update iiiftilesource.js

Fix Issue #55 "Tiles rendering issue..."
Update iiiftilesource.js
Update iiiftilesource.js
Update iiiftilesource.js
Update iiiftilesource.js
Update iiiftilesource.js
Update iiiftilesource.js
Update iiiftilesource.js
Update iiiftilesource.js
Merge pull request #154 from radix-pro/patch-1

Update iiiftilesource.js