do not apply any transformation to uploading payloads
removed `Content-Length` from upload (#8)

`Content-Length` header can cause failure of the `$upload` call in some browsers (http://www.w3.org/TR/XMLHttpRequest/#the-setrequestheader()-method)
Update README.md
Update README.md
Merge branch 'master' of github.com:ninjatronic/angular-kinvey