Fix #217, Add support for IO objects set as Attachment#content

[awj]

For non-binary files, this will re-encode the content as UTF-8 to match the expected type on the server.

Trying to use the smallest amount of the IO interface required so custom file-like objects more reliably work as expected.

[thinkingserious]

@awj

We have not been able to merge your Pull Request, but because you are awesome - we wanted to make sure you could still get a SendGrid Hacktoberfest shirt.

Please go fill out our swag form before Nov 5th and we will send the shirt! (We know that you might have tried this before and it didn’t work, sorry about that!)

You have till Nov 5th to fill out this form in order to get the Hacktoberfest shirt!

Thank you for contributing during Hacktoberfest! We hope to see you in the repos soon! Just so you know, we always give away a SendGrid shirt for your first ever non-Hacktoberfest PR that gets merged.

[clee]

LGTM

[thinkingserious]

Hello @awj,

Thanks again for the PR!

We appreciate your contribution and look forward to continued collaboration. Thanks!

Team SendGrid DX