Returns client response from upload_file

[aweidner]

Fixes #82

The only thing I'm not sure of here is the testing. I'm not a fan of having multiple assert statements in the same test cases but I don't want to duplicate the existing test code unnecessarily. Thoughts?

[HurSungYun]

I really want this. Thanks for fix it

[ricbartm]

@aweidner I'm interested on this to be reviewed by upstream too. Would you mind to tag the issue with the label "needs-review" to bring better visibility over it?

[aweidner]

@ricbartm Seems only those with write access to the repository are allowed to apply a label to a pull request. I'd love to get this reviewed if possible though, it has been open for a while now.