Release 2.0.0

[lionel-]

Includes #230.

I ran revdep checks again (for magrittr, dplyr, tidyr, and purrr, about 3000 packages) and found 6 remaining failing packages. Three of them were already found in a previous run and the authors were notified or provided a fix at that time (about two months ago):

• datamaps (fix at https://github.com/JohnCoene/datamaps/issues/2)
• rcrtan (fix at https://github.com/gtlaflair/rcrtan/pull/5)
• tidytidbits (notified by email)

Three failures are new:

• jqr (fix at https://github.com/ropensci/jqr/pull/82)
• reproducible (issue at https://github.com/PredictiveEcology/reproducible/issues/169)
• sketch, which I can't reproduce locally

I ran checks on win-builder, r-hub (including sanitizers and rchk) and found no issues.