Parallel builds--idea for next year

[seandavi]

For next year, it would be useful to develop a parallel build strategy to use multicore where possible and minimize rebuilds when not needed. Knitr caching helps, but particularly when running in an environment where the underlying code and R are not changing, remaking .md from .Rmd is wasteful.

[LiNk-NY]

Thanks Sean @seandavi,
Ideally, we'd have a builder (based on a docker image) with a webhook that will rebuild the book (in parallel) when there's a new commit.
I agree with the remaking .md from .Rmd is wasteful.
.md is an intermediate file and perhaps, the wastefulness can be resolved via markdown.