allow extra parameters for upload

There was no way to send (for example) the `text` parameter in `bot.upload()`
or `bot.uploadByUrl()`, so I modified it to allow sending an object in place
of summary (comment), which will then be added to the parameters sent with
the request.
Add a badge with NPM package version
Merge pull request #23 from Survos/extra-params-for-upload

allow extra parameters for upload
README: remove TODO section
0.3.8