added retry logic to HTTP requests

[jameslamb]

Thanks for this awesome project!

In this PR, I'd like to propose swapping out calls to httr::GET(), httr::PATCH(), etc. with httr::RETRY(). This will make the package more resilient to transient problems like brief network outages or periods where the service(s) it hits are overwhelmed. In my experience, using retry logic almost always improves the user experience with HTTP clients.

I apologize for the whitespace changes. I have my editor set to trim excess horizontal whitespace when I save files. If you'd like me to revert those please let me know.

[cpsievert]

Thank you for the PR, and sorry for delayed response!

That'd be great if you could revert the whitespace changes. Also, I think you missed this call to httr::VERB()

[jameslamb]

Thanks. I've reverted all of the whitespace changes and replaced the httr::VERB()

[cpsievert]

Sorry for the delay in getting this merged @jameslamb, this is looking good, and I'd be happy to take it on. Just a couple minor nitpicks:

• terminate_on was added in httr 1.3.0, so lets do httr (>= 1.3.0) in the DESCRIPTION file.
• Please use trailing commas (instead of starting a new line with a comma).

[jameslamb]

Sorry for the delay in getting this merged @jameslamb, this is looking good, and I'd be happy to take it on. Just a couple minor nitpicks:

• terminate_on was added in httr 1.3.0, so lets do httr (>= 1.3.0) in the DESCRIPTION file.
• Please use trailing commas (instead of starting a new line with a comma).

will do, thanks for the review!

[jameslamb]

Ok I just made the requested changes in 1bf6a4a. I've also rebased to master to catch changes that have happened since this was opened.

[cpsievert]

Awesome, thank you! One last request: could you add a NEWS.md item (under improvements)?

[jameslamb]

Sure! Just added in 0f1f181

I also fixed a missing comma from my last commit, which I think was the reason Travis was ❌