Allow aborting of jqXHR through promise.abort

The jqXHR object contained in the promise is overwritten by a promise object lacking an abort method via chaining `_onSend().then`.

Instead, jqXHR should be retained as a jqXHR even though the promise methods can be attached to it.

Try using:

    $("input").fileUpload().fileupload("send" {files: element}).abort()

to get an error that the `abort` method does not exist in this context.
Use $_REQUEST instead of $_GET for the file name param getters.

Thanks @vvinhas for the comment:
https://github.com/blueimp/jQuery-File-Upload/commit/f44f773c9c3e400b420
c8a5de7760bf3b4d652ce#commitcomment-6606586
Don't throw an error if flushing the output buffer fails. Closes #3201
Updated version number for last commit.
Fix for Issue and bug #3181 - drag drop 100 file limit
Merge pull request #3193 from ajcrites/abort-method

Allow aborting of jqXHR through promise.abort
Updated devDependencies.
Updated version for last merge.
Merge pull request #3226 from AllisonLamm/master

Fix for Issue and bug #3181 - drag drop 100 file limit
Merge branch 'master' of github.com:blueimp/jQuery-File-Upload
Updated version for last merge.
Patch release version fixing send API aborts and directory input reads.
Merge branch 'master' into gh-pages