Content-type headers are overriden when using put_attachment

[Louis-T]

Hi,

Thanks for this gem, it's quite useful.
I noticed that when using the put_attachment method (put_attachment(doc, 'nameWithoutExtension', image, content_type: 'image/jpeg')), the Content-type header is always set to text/plain.

I solved this slight problem locally by modifying the payload_from_doc to take into account the existing req[:header]['Content-Type'].

I don't know if it's wanted or not, but it can be problematic when using a name without extension.

[omensinger]

I stumbled across the same problem. Method "payload_from_doc" (in "connection.rb") overwrites the header in line "req[:header]['Content-Type'] = mime_for(req[:uri].path)", for whatever reason.