v2.0.0

Semantic command line interface tools

cli 2.0.0 has a new set of functions that help creating a CLI using a set
of higher level elements: headings, paragraphs, lists, alerts, code blocks,
etc. The formatting of all elements can be customized via themes.
See the "Building a semantic CLI" article on the package web site:
https://cli.r-lib.org

Bug fixes:

• Fix a bug in is_dynamic_tty(), setting R_CLI_DYNAMIC="FALSE" now
  properly turns dynamic tty off (#70).