FAQ - add these

[aahoyt]

More questions that have come up. In next FAQ revisions, make sure these are addressed if not already- -residence time calcs vs raw data -pmC to fraction modern -collection year vs AMS measurement year -analytical uncertainty vs std dev

[jb388]

Also:

• users interested in contributing code should run the devtools::check() fx to make sure that their code passes the CRAN checks
• how to enter data described as being from the same profile but with distinct depth intervals, e.g. pro_1 has layers 0-5, 5-10, 10-30, but also has layers 0-10, 10-20 20-30. This can come up with combined depths for certain analyses, e.g. to save $$; or could come from a pit with multiple samples extracted. These profiles with overlapping layers present a challenge for analysis.