file upload via <iframe> for IE8
use encodeURI() instead of the deprecated escape()
config.sessionId is in this.shinyapp instead of this
use uploadie instead of upload2 because of  regexec("^/([a-z]+)/([^?]*)" earlier ([a-z]+ won't match upload2)
if evt.target.files is undefined, it is probably IE8; we will use iframe from POST to upload the files later
return a valid response temporarily
the key problem with the form submission was that the name was missing
the iframe does not need src, and we should attach the onload event after it is appended to body, otherwise it will be destroyed immediately
parse the multipart form data POSTed and save the file info in .input
Force IE8 uploads to kick off reactive flush
Add import for mime
install mime for travis ci
IE8 does not support iframe.onload; we need to use .attachEvent() instead
I do not see why this needs to be changed
use the IE8 file uploader only for IE
do not store the FileUploader in el.data('currentUploader') for IE (it does not have the .abort() method)
fileInput() works for IE8/9 now, but they do not support multiple files
add a news item for file uploading in IE8/9
use typeof(x) === 'undefined' instead of x === undefined
Merge pull request #598 from yihui/feature/ie8-uploads

IE8/9 file upload