Add "Get PDF" Button to Door43 Pages

[jag3773]

Story

As a user I want to get a PDF from my Door43 user/repo page so that I can download, use, edit and/or share the resource offline.

Notes

For all of the rendered content on the door43.org/u/ pages, we want to add a "Get PDF" button that will use #11 to generate the PDF.

This button should do the following:

• Check to see if a PDF exists for the latest commit (by checking /u/[user]/[repo]/[short_commit_hash]/pdf/[repo_name_timestamp].pdf).
• If above fails,
  • Hit the API endpoint to ask for a PDF
  • Let the user know that it will take a few seconds
  • Start the download when the generation is finished

Optionally, we may want to allow the user to be emailed the PDF link if they do not want to wait.

[jag3773]

Issue moved to unfoldingWord-dev/hubot #53 via ZenHub