:sessionId/file - allow file upload from machine running a test to a remote selenium standalone RC

Pretty much taken directly from:
http://stackoverflow.com/questions/10559728/uploading-files-remotely-on-selenium-webdriver-via-php/10560052?noredirect=1#comment21729813_10560052

Not sure how coding standards are supposed to work.

It's been working for me for simple things, like transferring a single picture. There seems to be a file size limit though (I've only tried up to around 5MB).