Allow file-name and description to be set on all content parts

[bo-chen]

This allows file-name to be set on all parts of the message, not just attachments. Here's an example of including some csv data in an email:

(send-email
  {:from "bo@"
   :to addresses
   :subject "hi"
   :body [{:type "text/plain"
           :content "I attached a csv"}
          {:type "text/csv"
           :file-name "data.csv"
           :content csv-content}]})

[charles-dyfis-net]

Could you add test coverage?

[bo-chen]

Added

[drewr]

Thanks @bo-chen! Added a way to keep the dotos in there in 8a2de00. Mind merging it in? git fetch && git merge --no-ff origin/thread-conditionals.

[bo-chen]

Merged the contribution and removed clojure 1.3 and 1.4 dependency as discussed.

[drewr]

Looks good :+1:

I've invited you to collaborate, so you can merge when ready!

[bo-chen]

Thanks it's in!