fix 'C:\fakepath\' in files uploaded via add-module-item

test plan: using Chrome 36, upload a file via the "Add Module Item"
dialog on the modules page. the module item should match the file name
and should have any path, fake or otherwise, stuck in front of it.

fixes CNVS-14380

Change-Id: I050ea93797468636b3d35846cf54ebe3d6c302cc
Reviewed-on: https://gerrit.instructure.com/38047
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jon Willesen <jonw@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>