Accept a threshold param for larger file uploads.

Hello @evansolomon, 

Please review the following commits I made in branch 'tyler-threshold-param'.

fda4e2945a9a5db619a98370617265bfa6342d8b (2013-09-26 21:00:00 +0000)
Accept a threshold param for larger file uploads.

Check list:


R=@evansolomon