orgadish

@jennybc I have found that I use `run_examples()` / `run_example()` a lot when first developing my packages, i.e. when I'm still working out the kinks in new functionality. You're right...

Or perhaps even better create an `archive_filter` function that does the first part. Ideally, it would even return an archive object that it could be passed directly to `archive_extract`, but...

@gaborcsardi I wasn't sure if you meant to add it just for the `archive_extract` manual, or the README, but I added to both. If you intended something else, please let...

@gaborcsardi In creating this PR and running the various `devtools` commands to build the package, there were some changes to the `cpp11` files that seem to just involve reordering of...