Update UploadServlet.java

When i tried to upload a big file over 2.7G, the server give me an Exception " Negative Seek Offset".
This issue is due to integer overflow.
Added pause() method for ResumableFile
Merge pull request #145 from pawski/feature

Added pause() method for ResumableFile
Merge pull request #144 from DevinTan/master

Update UploadServlet.java