Changelog • pinboardr

Checked if all functions have export and examples
Checked against multiple R versions on mac
Clarified some things in Readme

Added a NEWS.md file to track changes to the package.
implemented tags endpoints
implemented authentication and basic url building
adding tests for all non web facing functions
implemented pb_posts_suggest, pb_posts_dates, pb_posts_recent, pb_posts_delete
added doc for authentication ?authentication
added convenience function for extracting tag
replaced authentication with authentication
implemented user endpoints
implemented notes endpoints