Replace Google Doc Preview with Predoc

CANVAS-205
Fix to remove scroll bars in the document preview
Merge pull request #82 from va7map/canvas205

CANVAS-205 Replace Google Doc Preview with Predoc
Fix inability to upload files on Flashless browsers

Affected browsers are Firefox (including version 21) and Safari
(including version 6).
Merge pull request #83 from va7map/fix-flash_upload

Fix inability to upload files on Flashless browsers