ctkremer/growthTools: First public release

This is the first public release of a stable version of the growthTools package. No fundamental changes to the code, but it tidies up some old issues and provides improved documentation. A new release is anticipated in the next ~1 month with bigger changes, but this version is being released and archived as several manuscripts in prep rely on this older version of the package and I want to provide a DOI. (removed /user/ folder prior to archiving)