Add for support file upload 

I want to do load-test with file upload,so I changed some codes. 
Maybe this commit is not best,but works.

    del options['headers'] 
- https://github.com/anarcher/boom/pull/new/master#L0R99

When I use options['headers'], requests request without files.
I don't know why requests can't do file-upload.

If you have better idea than this commit, I welcome to ignore this pull request. :-)